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
Load inventories asynchronously (requires updating projects to .Net 4.5)
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- Updates outdated EEconTradeResponse message types.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)
Adds User Handler feedback on bot's trade request accept/decline.
Merge pull request #529 from BlueRaja/AsynchronousInventories

Load inventories asynchronously
Back to .NET Framework 4.0 Patch

Changed:
* Task.Run [.NET Framework 4.5] to Task.Factory.StartNew [.NET Framework
4.0]
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
Merge pull request #531 from FrozenHaxor/master

Adds User Handler feedback on bot's trade request accept/decline.
add InventoryToken to Item
Merge remote-tracking branch 'upstream/master'