Extend and/or queries to return multiple result types

Created by: rvantonder

Example, this query newRouter or file:router.go should work and return both results types.

https://sourcegraph.com/search?q=repo:%5Egithub%5C.com/sourcegraph/sourcegraph%24+newRouter+or+file:router.go&patternType=regexp

and

similarly file:main.java AND reserved should work as an alias for file:main reserved

This is separate from expanding and/or queries to arbitrary scope (nested queries). It concerns the type of the expression result.

(This is a significant chunk of work that I've had in mind, but hadn't create an issue yet. Will likely happen in one or two iterations in future at the current pace of things.)