Use bash_bootstrap for the bootstrap build.

* don't build the in-tree bash.
* bash doesn't need to be a mandatory package, it's now a dependency of
the haiku package.
moves /bin/sh to bash packages.

* bash is a mandatory package.
Move Geolocation to kits/shared and make it private.
Look for private key of default geolocation service.

* Let the jamfile set HAVE_DEFAULT_GEOLOCATION_SERVICE_KEY if the
  header that is supposed to contain it is found in src/kits/shared
  (which isn't the case for normal builds).
* In case HAVE_DEFAULT_GEOLOCATION_SERVICE_KEY is set, include the
  corresponding header and activate Mozilla's geolocation service with
  the key defined in that header.
  
This procedure should enable buildbot to create nightly images without
exposing the private service key.