taserver release v2.6.0

Features added:

• added script to facilitate upgrading to later releases (upgrade.py)
• implemented a new verification mechanism that uses email
• implemented map voting
• authbot now keeps connecting to hirez servers even when it says credentials are invalid
• make game server process use 0% CPU while noone is playing there
• various documentation updates

Bugs fixed:

• fixed a login server crash caused by sending a private message while someone is logging in
• always give OOTB loadouts to players playing on OOTB servers
• fix non-working motion sensor in OOTB
• fixed a game server crash caused by joining during a map switch
• download_gotylike.py now downloads from Griffon26's fork. This fork has fixes to be
  more close to the original GOTY.

Compatibility notes:

• this release is not backwards compatible; both login server and
  game servers must be upgraded to v2.6.0 simultaneously.
  After the upgrade a new controller must be downloaded by running
  the download_compatible_controller.py script.