Added Sqlite.Mac, update to Profile 158, WP80, remove old WP.CS, updated...

... formatting and code from latest sqlite-net, nuget package restore, sqliteasync

Not quite ready for direct merging yet, as it contains a nuget reference to our nuget servers. Once the Mac pkgs are being generated by the main MvvmCross project, we should refer to that then it will be ok.

In particular SQLiteNet is updated so that the formatting is very close to the sqlite-net project. This makes comparisons a bit easier as they update their project.