New map generator added (and SQLite, messed up the commits at that time...) (import from temporary git repo)

Moved some mapnode content stuff from mapnode.{h,cpp} and digging property stuff from material.cpp to content_mapnode.{h,cpp}

Note: can't test this properly yet - may be fixes to follow

--HG--
extra : rebase_source : e2d41621018f886d340c7847b29240042d4412ac

Fixed a temporary solution of server shutting down to an assert(0) when a too large block metadata is sent to an old client

Made a proper queued thread to client for handling some block mesh updates. Also made client mutex-free to allow easier adding of new stuff.

Modified block mesh generation to have clearer input and output. Instead of being a messy object oriented cludge, it now is a messy cludge with separate parameters.