Improve SteamWeb to work with GET requests
Use SteamWeb.Fetch() properly, rather than shimmying the request-params into the URL.

Also, fixed spelling error.
BUGFIX: Private inventory causing crash sometimes
Remove annoying console "error" - also don't use '0' as an error-defindex (that's a valid defindex)
Eliminate compiler warning (whoops)
Remove more pointless console errors
Wrapped some more things in "using"s, plus some minor code cleanup
Moved cookies to SteamWeb.  As a result:
* SteamWeb is no longer a static class
* Backwards compatibility has been broken.  You now need to pass SteamWeb to Inventory and GenericInventory
* Fetching inventories set to "friends only" should now work.
Merge branch 'JessecarMaster' into WebAndForeignInvImprovements

Conflicts:
	SteamBot/Bot.cs
	SteamBot/UserHandler.cs
	SteamTrade/SteamWeb.cs
Merge SteamWeb fixes