[267] Added commands for tickrate, sendrate, bwlimit

Allow server configuration of tickrate (default 30/sec), rate of updates
sent to clients (default 20/sec) and bandwidth limit per player (
default 25kb/sec)

Note: you should keep sendrate < tickrate <= mr, and interp >=
2/sendrate

Also with 267 those values ( oncluding mr and interp) will be synched correctly at client connect