* modest-tny-account-store.c:

* modest-tny-account-store.c:
  - keep some ptr around in ModestTnyAccountStorePrivate* so we don't leak
  - update all the data returning functions to use that
  - free them in the finalize, add some cleanup functions
  - add TnyDevice get_device stub
  - add some sanity checks
  - I merged my changes with the ones from Nils/Silvan

Still, it still *crashes*, like it does in the version without these changes.
  So I'm still checking this is, as things have not gotten *worse*.

  Both old and new versions do:

   (modest:17203): GLib-GObject-WARNING **: invalid cast from `ModestTnyAccountStore' to `TnyAccountStore'

(modest:17203): GLib-GObject-WARNING **: attempt to retrieve private data for invalid type 'TnyAccountStore'

   Will research this further.

pmo-trunk-r44