different treatment of internal/external init options

Realised the [other day](https://github.com/ractivejs/ractive/pull/1381#issuecomment-60323677) that we should have a cleaner separation between the initialisation options that a developer would use with `new Ractive(...)` or `Ractive.extend(...)`, and the options Ractive uses internally when creating inline components.

This is a start in that direction, though it bumps up against #1411, so we should lock that down first before merging this