Fix trade offers

Fix trade offers still using non-HTTPS requests.
Merge pull request #661 from StoneWolf/master

Fix trade offers
Update OfferSession.cs
Merge pull request #664 from vudung45/master

Update OfferSession.cs
Merge pull request #651 from WildCard65/Steamkit2Fixes

Fixed Steamkit2 issues
Fix item removal.
Merge pull request #673 from scholtzm/RemoveItemFix

Fix item removal from trade offer.
Updated packages again.

Updated Steamkit2 to V1.6.2
Updated Json.Net to V6.0.6
Merge remote-tracking branch 'BlueRepo/WebAndForeignInvImprovements' into MyBot

Conflicts:
	SteamBot/Bot.cs
	SteamTrade/TradeOffer/OfferSession.cs
Merge branch 'MyBot' of https://github.com/WildCard65/SteamBot into MyBot