CommonReactiveSource allows section info list to be updated.

Note that now we require at least IReadOnlyList instead of
just IEnumerable.  I argue that this is the morally correct
thing to do since it allows us to ditch .ToList().
Reactive{Collection,Table}ViewSource now are IReactiveNotifyPropertyChanged.

Uses copy-paste from ReactiveNSView.
Stronger-typed CommonReactiveSource.
New Data property for Reactive{Collection,Table}ViewSource.
CommonReactiveSource now reacts to section changes.
Fix a couple of boring bugs.
Oh, snap!
New extension methods for Reactive{Collection,Table}ViewSources.
Do not try to automagically convert strings to NSStrings.

IMHO this is the morally correct action to take.  iOS is going
to compare strings by reference, so:

  - Original code by @paulcbetts used a cast from string to
    NSString.  I have no idea how it works, but it does seem hackish.

  - I had modified the code to use new NSString(), which in
    hindsight obviously will not work.

  - This new version does not autoconvert anything at all, thus
    the process is transparent and does not rely on internal details.
Merge remote-tracking branch 'origin/pr/402'
What's this silly goosery
Remove bogus XML doc genning from RxUI.Events MonoMac