[[ ImageLoader ]] Create MCImageLoader class interface
[[ ImageLoader ]] Reimplement MCImageDecode<format> functions as equivalent MCImageLoader subclasses
[[ ImageLoader ]] Update Image import functions to use MCImageLoader
[[ ImageLoader ]] Fix bug in IO_fgets causing inifinite loop when loading xpm file
[[ ImageLoader ]] Update Android, iOS, Linux & OSX server build files
[[ ImageLoader ]] Update Windows engine & server build files
Merge remote-tracking branch 'runrevian/refactor-imageloader' into bugfix-13021

Conflicts:
	engine/engine.xcodeproj/project.pbxproj
	engine/src/ifile.cpp
	engine/src/igif.cpp
	engine/src/iimport.cpp
	engine/src/image.h
	engine/src/image_rep_encoded.cpp
[[ Bug 13021 ]] Rework MCImage::lockbitmap() MCImage::draw() to allow density-mapped images to have mismatched scale & image sizes.
[[ Bug 13021 ]] Modify MCDensityMappedImageRep::GetGeometry() to return logical image size for the whole set.
[[ Bug 13021 ]] Remove unused density & scale methods from MCImage & MCImageRep classes
[[ Bug 13021 ]] Add MCGRectangleScale variant with horiz/vert params
[[ ImageLoader ]] Add frame count to information read from the header.
[[ ImageLoader ]] Use header framecount for MCEncodedImageRep::GetFrameCount()
Merge remote-tracking branch 'runrevian/refactor-imageloader' into bugfix-13021

Conflicts:
	engine/src/ibmp.cpp
	engine/src/igif.cpp
	engine/src/ijpg.cpp
	engine/src/image_rep.cpp
	engine/src/image_rep.h
	engine/src/imageloader.cpp
	engine/src/ipng.cpp
[[ Bug 13021 ]] Add bugfix note
Merge branch 'develop' into bugfix-13021

Conflicts:
	engine/src/idraw.cpp
	engine/src/image.cpp
	engine/src/image_rep.cpp
	engine/src/image_rep_densitymapped.cpp
	engine/src/image_rep_encoded.cpp
	engine/src/imagelist.cpp
[[ Bug 13021 ]] Minor formatting changes
Merge remote-tracking branch 'ian/bugfix-13021' into bugfix-13021
[[ Bug 13021 ]] Split image frame density into x & y scale components
Merge remote-tracking branch 'ian/bugfix-13021' into bugfix-13021
Merge branch 'bugfix-13021' into develop