Support for overriding victory/defeat conditions from h3m map or
campaign:
- new file MapFormatJson that implements small subset of Json map
format, as described on wiki
- vcmi will read overrides from file config/mapOverrides.json (currently
empty)
- Json writer for logical expressions

TODO: write data for map overrides


git-svn-id: http://svn.code.sf.net/p/vcmi/code/trunk/@3692 4dfc6b2a-8b31-0410-aa91-d6c70e3ac834