Refactor _cparser_get_with_deprecated()

We have two copies of this method with the only difference being the
use of the multi kwarg. Obviously, it makes sense to combine the two.

Change-Id: I48fccccf32d839a9d443c638e0058354e26a6af9
Allow MultiConfigParser get from mutliple sections

MultiConfigParser.get() takes a section name and a list of option names.

In order to support aliases of options which span multiple groups, we
need to be able to look up from multiple sections. We can easily do this
by changing MultiConfigParser.get() to take a list of (section, name)
tuples.

Change-Id: I50656c021669ccb947ceb56dfcf37d3fffcba194
Merge "Refactor _cparser_get_with_deprecated()"
Merge "Allow MultiConfigParser get from mutliple sections"