* As UCB is only ever initialized with "Local"/"Office", remove this
  configuration vector completely.  The "create" ctor creates an instance
  internally initialized with those "Local"/"Office" keys.  Special (test) code
  can still instantiate an uninitialized one via plain createInstance.  And for
  backwards compatilibity process startup still ensures to create an initialized
  instance early, in case there is still code out there (in extensions) that
  later calls plain createInstance and expects to get the already-initialized
  (single) instance.

* XInitialization is an "implementation detail" of the UniversalContentBroker
  service, do not expose in XUniversalContentBroker.

* ucbhelper/configurationkeys.hxx is no longer needed and is removed.

* ucbhelper/contentbroker.hxx is an empty wrapper and is removed; however, that
  requires ucbhelper::Content constructors to take explicit XComponentContext
  arguments now.

* The only remaining code in ucbhelper/source/client/contentbroker.cxx is
  Android-only InitUCBHelper.  Is that relevant still?

Change-Id: I3f7bddd0456bffbcd13590c66d9011915c760f28