* [Core, UWP, Android] support TabStop/TabIndex
* removing linq
* add iOS / MacOS implementation
* add WPF implementation
fixes UWP implementation
* - addressing comments
- improve test
- optimizations
- added previous tab direction in same tab group
* addressing comments
* [Android] support tabstop for pickers
* - moving shared code to a static class
- removed reflection
* ITabStop -> changed to internal, renamed, added in to fastRenderers
* Update ITabStop to be public
* Repro of modal-over-map-crash issue
* Automated test for maps modal crash
* Generate Ids for all Renderer Views on Android
* Add Ids for PageContainer and PageRenderer
* Remove TODO comment
* Verify fast renderers aren't disposed before querying Id
* Remove InternalsVisibleTo from Core to XF.Platforms.*
* Changes per Jason's code review
* Move LockableObservableListWrapper to internals namespace
* Changes per Stephane's code review
* update docs
* Touch code to get CI to run tests
* Rebase; Update documentation