- reorganized internal filesystem structure - all files from one mod are
now grouped in same FS node
- modhandler will now calculate crc32 checksum for each mod
- modhandler now knows validation status of each mod
todo - use checksum to determine mods that have not changed since last
start and disable validation for them.
- split JsonNode.cpp into JsonNode and JsonDetail files
- validation should be notably faster (at least 10% faster loading)
- support for "format" field, allows checking existance of files.
- minor fixes in schemas
- msk/msg files are now optional
