Initial implementation of combining commands
Write tests to make sure that async canExecute is represented correctly
Add parameter to allow parent to specify a canExecute as well
Merge pull request #382 from reactiveui/combined-commands

Combined commands
- Implemented basic command binding support for Android View derived classes
- Bumped Android Target Framework to 15 since there are pretty much no vanilla 4.0 out in the wild

Conflicts:
	ReactiveUI.Events/Resources/Resource.Designer.cs
Move FlexibleCommandBinder to be shared
Merge pull request #371 from reactiveui/android-binding-improvements

- Implemented basic command binding support for Android View derived cla...