Add external extensions to the extension list

and allow them to choose their default state with Plugin.DefaultState.
Small error

When the game's starting we should still halt CheckGameStart.
Ban hooks

so people can make plugins that send bans to a website for syncing.
Fixed a script error in saving score data

The kills value is sometimes nil.
Error reporting

Reports to my server at the end of a round with any errors that occured.
Don't send a report if there's no errors!
More reliable reserved slot tag setting

Should avoid duplicate tags.
Changes to improve ELO vote reliability

Gets the targets when we have a successful response from NS2Stats,
rather than using potentially old and incorrect information (which can
cause errors if the player entity in question no longer exists).
Fix for issue with mode 2 of pregame

It was running the 2 commander start timer alongside the 1 commander,
leading to 2 game starts.
Fixed another small bug with ELO sort

It now doesn't assume there's 8 players sorted by ELO every time.
Protected call console command functions

So we report catch and report errors from them too.
Limit the size of error data

I doubt there'd ever be this much, but it's better to be safe.
Merge pull request #228 from Person8880/develop

Lots of fixes