Drop concatenated title of 'add' dialog
As for now the default title of 'add' dialog is set to something
like 'Add ${entity}', where 'entity' is also translatable text.
Such construction is used via method 'adder_dialog' of Entity
for the all 'Add' actions.
This leads to a bad quality translation and should be changed to
an entire sentence.
From now a mentioned title is taken from a spec and should be
specified explicitly.
Fixes: https://pagure.io/freeipa/issue/7707
Reviewed-By: Serhii Tsymbaliuk <stsymbal@redhat.com>