Big images: first step before hdf5 images

Add:

- concept CImageCacheReadPolicy.h with 2 models : ImageCacheReadPolicyLAST and ImageCacheReadPolicyFIFO
- concept CImageCacheWritePolicy.h with 2 models : ImageCacheWritePolicyWT and ImageCacheWritePolicyWB
- test program : testImageCache.cpp

- concept CImageFactory.h with 1 model : ImageFactoryFromImage

- very simple sample class TiledImageFromImage with test program : testTiledImage.cpp