variety of enhanements

This PR a) facilitates the indexing of nested types, such that if elements sprog located at my.firebaseio.com/sprog are nested with an elastic search type, so it would be mine.bonsai.org/myindex/foo/sprog or whatnot, the indexing via flashlight can be mapped correctly.

The parse function is also adapted to use promises, so that, e.g., a large body payload stored in s3 referenced from firebase can be indexed for fulltext search.

Path configuration is factored out to be separate from app configuration, so that it's easier to commit changes upstream from a working installation.

A command line argument is added for disabling watching of the /search path, if a user wants to hit the ES server directly rather than proxying it.  This PR is not quite ready for merge, but I wanted official feedback.

Cheers!