Make flag strings clear specified flag with 'no' prefix

Remove flagmask field from set_mapgen_params table
Add small bits of needed documentation
Tune block emerge and sending parameters to more aggressive values
Cleanup client init states by bumping protocol version
Don't use TOSERVER_RECEIVED_MEDIA but TOSERVER_CLIENT_READY as indicatio for client ready
Handle clients with protocol version < 23 (almost) same way as before
Make client tell server about it's version
Add client state to not send bogus player position updates prior init complete
Add access to statistics information (peer connction time,rtt,version)
Fix clients standing stalled in world while preloading item visuals (new clients only)
Add get_player_information to read client specific information from lua