Add multi-frame handling.

- Exif of all frames are displayed in the Editor's Exif tab (without
separator)
- isHDR and isPixelShift is added to the data files stored in cache
- In the Editor panel, the QuickInfo frame display the HDR and
PixelShift information, as well as the number of frame and bit-depth for
HDR image
- the number of frame is provided by dcraw. If not set, it is provided
by the Exif's main IFD count
- the PixelShift information (for Pentax as of now) is provided by
looking at the Exif informations
- the HDR information is provided by the Exif information of the first
frame for Pentax raw files, or by the bitspersample, sampleformat and
compression tags for other files

TODO: add icons to the thumbnails to tag HDR and PixelShift files.

rtengine/stdimagesource.h

@@ -68,9 +68,9 @@ public:
     void        getFullSize (int& w, int& h, int tr = TR_NONE);
     void        getSize     (const PreviewProps &pp, int& w, int& h);
 
-    ImageData*  getImageData ()
+    FrameData*  getImageData (int frameNum)
     {
-        return idata;
+        return idata->getFrameData (frameNum);
     }
     ImageIO*    getImageIO   ()
     {