Fix: web-related crashes

Edited:
Bot.cs - BackgroundWorkerOnDoWork(...)
Added: other exceptions + restart
Improving error messages and fixing non-restarting bug
BUGFIX (to laggingpyro's stuff): Not sure what the purpose of this was, but it appears to cause an infinite loop sometimes
Adds Clan Related Handlers and Functions

What this does:
- Adds OnClanAdd() function to UserHandler.cs, SimpleUserHandler.cs, and
AdminUserHandler.cs.
- Adds InviteUserToClan() function to Bot.cs.
- Adds DeclineClanInvite() function to Bot.cs.
- Adds AcceptClanInvite() function to Bot.cs.
- Adds ClanMessages.cs that contains all SteamMessages need for new
actions.
- Filters out Clan Invites from Friend Invites.
- Adds a Clan list that contains all Clans the Bot is in.
- Fixes some spelling errors.
- Updates outdated EEconTradeResponse message types.
Renamed "Clan" to "Group," as per @geel9's request on the original pull-request
Moved group-related messages to their own folder (similar to the TF2GC folder)
Whoops!  Missed a few functions (renaming clan --> group)
Merge pull request #530 from BlueRaja/SteamGroupFunctions

Add functionality for Steam Groups
Merge pull request #534 from gabrielmtzcarrillo/net40

Back to .NET Framework 4.0 Patch
Removed obsolete reference to SteamKit's EChatEntryType.Emote
Merge pull request #536 from FunkyLoveCow/RemoveObsoleteWarning

Removed obsolete reference to SteamKit's EChatEntryType.Emote
Merge pull request #528 from BlueRaja/laggingPyroFixes

Keep bot running after a crash