[Android] Convert Modal Implementation over to using Dialog Fragment

[PureWeen]

Description

Right now we use a somewhat awkward mechanism to do modals in android. We basically add a view to the decor view on top of everything. This requires a ton of custom code to make sure everything operates successfully.

I'm fairly sure if we just switched to Dialog Fragments we could remove most of that code and then it would all just work more naturally.

I have a branch here

That mostly works but just needs a bit more testing and cleanup