Fixed reading of layer's "mask_data" and "global_mask_info" fields
Fixed reading of "global_mask_info" and "tagged_blocks" sections
Fixed reading of layers and layer mask data
Implemented decoding of known undescribed descriptor's types. Some more may exist
Removed duplicated constants
Some TYPOs fixed
Misc additions and corrections to layers reader
Merge pull request #29 from EvgenKo423/master

Big work on the mistakes