fs/cromfs: Fix a error in reading partial compressed blocks. The LZF...

fs/cromfs:  Fix a error in reading partial compressed blocks.  The LZF decompressor does not support that operation.  Instead we have to decompress full block into a temporary buffer and copy out the parts that we need.  To compensate for the performance hit, a caching mechanism was added so that we do not have to read the same block repeatedly.  Unrelated:  Also updates some README files.