Added SQLite mappings

ISQLiteConnection and ITableMapping
Merge pull request #129 from asednev/vnext

Added SQLite mappings
Fix for abstract bindable SimpleTableViewSource
Merge branch 'vnext' of https://github.com/slodge/MvvmCross into vnext
Merge branch 'vnext' of github.com:slodge/MvvmCross into vNextDialog