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.

rtgui/inspector.cc

@@ -59,7 +59,7 @@ InspectorBuffer::~InspectorBuffer() {
 //int InspectorBuffer::infoFromImage (const Glib::ustring& fname)
 //{
 //
-//    rtengine::ImageMetaData* idata = rtengine::ImageMetaData::fromFile (fname, nullptr);
+//    rtengine::FramesMetaData* idata = rtengine::FramesMetaData::fromFile (fname, nullptr, true);
 //
 //    if (!idata) {
 //        return 0;