FramesData: Don't leak allocated frames, and remove unused functions

Valgrind report:

```
14,960 (11,544 direct, 3,416 indirect) bytes in 37 blocks are definitely lost in loss record 20,483 of 20,540
   at 0x4837DEF: operator new(unsigned long) (vg_replace_malloc.c:334)
   by 0xC06963: rtengine::FramesData::FramesData(Glib::ustring const&, std::unique_ptr<rtengine::RawMetaDataLocation, std::default_delete<rtengine::RawMetaDataLocation> >, bool) (imagedata.cc:1121)
   by 0xBD774F: rtengine::DFManager::addFileInfo(Glib::ustring const&, bool) (dfmanager.cc:380)
   by 0xBD6E90: rtengine::DFManager::init(Glib::ustring) (dfmanager.cc:303)
   by 0xC3EC5D: rtengine::init(rtengine::Settings const*, Glib::ustring, Glib::ustring, bool) [clone ._omp_fn.0] (init.cc:93)
   by 0x897CABD: gomp_thread_start (team.c:120)
   by 0x89B7A9C: start_thread (in /usr/lib/libpthread-2.28.so)
   by 0x8ACCB22: clone (in /usr/lib/libc-2.28.so)
```

rtengine/imagedata.cc

@@ -809,11 +809,6 @@ unsigned int FramesData::getFrameCount () const
     return dcrawFrameCount ? dcrawFrameCount : frames.size();
 }
 
-FrameData *FramesData::getFrameData (unsigned int frame) const
-{
-    return frames.empty() || frame >= frames.size() ? nullptr : frames.at(frame);
-}
-
 bool FramesData::getPixelShift () const
 {
     // So far only Pentax and Sony provide multi-frame Pixel Shift files.
@@ -1118,9 +1113,7 @@ FramesData::FramesData (const Glib::ustring& fname, std::unique_ptr<RawMetaDataL
 
                 // creating FrameData
                 for (auto currFrame : exifManager.frames) {
-                    FrameData* fd = new FrameData(currFrame, currFrame->getRoot(), roots.at(0));
+                    frames.push_back(std::unique_ptr<FrameData>(new FrameData(currFrame, currFrame->getRoot(), roots.at(0))));
-
-                    frames.push_back(fd);
                 }
                 for (auto currRoot : roots) {
                     rtexif::Tag* t = currRoot->getTag(0x83BB);
@@ -1142,8 +1135,7 @@ FramesData::FramesData (const Glib::ustring& fname, std::unique_ptr<RawMetaDataL
                 exifManager.parseJPEG ();
                 roots = exifManager.roots;
                 for (auto currFrame : exifManager.frames) {
-                    FrameData* fd = new FrameData(currFrame, currFrame->getRoot(), roots.at(0));
+                    frames.push_back(std::unique_ptr<FrameData>(new FrameData(currFrame, currFrame->getRoot(), roots.at(0))));
-                    frames.push_back(fd);
                 }
                 rewind (exifManager.f); // Not sure this is necessary
                 iptc = iptc_data_new_from_jpeg_file (exifManager.f);
@@ -1161,9 +1153,7 @@ FramesData::FramesData (const Glib::ustring& fname, std::unique_ptr<RawMetaDataL
 
             // creating FrameData
             for (auto currFrame : exifManager.frames) {
-                FrameData* fd = new FrameData(currFrame, currFrame->getRoot(), roots.at(0));
+                frames.push_back(std::unique_ptr<FrameData>(new FrameData(currFrame, currFrame->getRoot(), roots.at(0))));
-
-                frames.push_back(fd);
             }
             for (auto currRoot : roots) {
                 rtexif::Tag* t = currRoot->getTag(0x83BB);

rtengine/imagedata.h

@@ -20,6 +20,7 @@
 #define __IMAGEDATA_H__
 
 #include <cstdio>
+#include <memory>
 #include "rawimage.h"
 #include <string>
 #include <glibmm.h>
@@ -89,7 +90,7 @@ public:
 class FramesData : public FramesMetaData {
 private:
     // frame's root IFD, can be a file root IFD or a SUB-IFD
-    std::vector<FrameData*> frames;
+    std::vector<std::unique_ptr<FrameData>> frames;
     // root IFD in the file
     std::vector<rtexif::TagDirectory*> roots;
     IptcData* iptc;
@@ -102,7 +103,6 @@ public:
     void setDCRawFrameCount (unsigned int frameCount);
     unsigned int getRootCount () const;
     unsigned int getFrameCount () const;
-    FrameData *getFrameData (unsigned int frame) const;
     bool getPixelShift () const;
     bool getHDR (unsigned int frame = 0) const;
     std::string getImageType (unsigned int frame) const;

rtengine/imagesource.h

@@ -110,7 +110,6 @@ public:
         return 0;
     }
 
-    virtual FrameData*     getImageData (unsigned int frameNum) = 0;
     virtual ImageMatrices* getImageMatrices () = 0;
     virtual bool           isRAW () const = 0;
     virtual DCPProfile*    getDCP (const ColorManagementParams &cmp, DCPProfile::ApplyState &as)

rtengine/rawimagesource.h

@@ -168,10 +168,6 @@ public:
         return ri->get_rotateDegree();
     }
 
-    FrameData*  getImageData (unsigned int frameNum)
-    {
-        return idata->getFrameData (frameNum);
-    }
     ImageMatrices* getImageMatrices ()
     {
         return &imatrices;

rtengine/stdimagesource.h

@@ -69,10 +69,6 @@ public:
     void        getFullSize (int& w, int& h, int tr = TR_NONE);
     void        getSize     (const PreviewProps &pp, int& w, int& h);
 
-    FrameData*  getImageData (unsigned int frameNum)
-    {
-        return idata->getFrameData (frameNum);
-    }
     ImageIO*    getImageIO   ()
     {
         return img;