flickr: Remove obsolete and meaningless comment
flickr: Add the missing "Use for" string
owncloud: Fix and simplify the use of GtkGrid
exchange: Fix and simplify the use of GtkGrid
Fix and simplify the use of GtkGrid inside show_account

There is no need to use two grids -- only one should be enough.
To avoid breaking API and ABI during the freeze, we turn one of the
GtkGrid* arguments passed to goa_provider_show_account into a dummy.

One side-effect of this is that show_account is now a pure virtual
method without any default implementation. But that is fine, since
the default implementation was relatively trivial, and this is
supposed to be internal to libgoa-backend.so.

Fixes: https://bugzilla.gnome.org/706664
kerberos: Fix and simplify the use of GtkGrid