Adding support for inheriting chunks from _ViewStarts as part of host parsing

Fixes #881
This is pretty hard to customize, but at the same time we want all these to be very declarative, and not controllable through code (at least not very easily). Should we just make it a virtual property returning a string[]. And users can customize it (but not through startup.cs?) - Say we add a doc comment explaining the impact on design time.

Similarly below for the common methods for the base class.

I'm fine tracking this as another issue (and it's not that high of a priority)