webadmin: Allow to change version name of template

It is now possible to change the name of a template sub-version from the
template's edit dialog. Note that it is only allowed for sub-versions,
for base versions the version name is "base version" and the text box is
disabled.

Change-Id: I3c33a8b87f5df7e3dbc23bfcb97cc839b0b6b7bb
Bug-Url: https://bugzilla.redhat.com/1058501
Signed-off-by: Arik Hadas <ahadas@redhat.com>