Add setgame command, change config vars, add dynamic bot game status

[ldilley]

Proposed Changes

• Add dynamic Discord bot game status (closes #137).
• Replace terracord.xml configuration variables with meaningful names (closes #138).
• Add setgame command (closes #139).
• Add Terraria server name to dynamic Discord text channel topic update

[AppVeyorBot]

:white_check_mark: Build terracord 1.2.3.174 completed (commit https://github.com/FragLand/terracord/commit/1c42a1b850 by @ldilley)

[AppVeyorBot]

:white_check_mark: Build terracord 1.2.3.174 completed (commit https://github.com/FragLand/terracord/commit/1c42a1b850 by @ldilley)