Add group type 'pkgdb' for groups managing packages in pkgdb

With pkgdb2, we will allow FAS group to have commit on some packages, but only
the 'pkgdb' group will be allowed by pkgdb2 to have ACLs
Add method to query group by group_type
Add endpoint to query all the groups of a certain type.
Add pkgdb in the list of options for group_type
Fix typo in variable name
To return all the results, use all() not one()
Fix the correct method...
We need to know who is asking to be able to filter what he is allowed to see
The template requires that we use search
Add SQL update script adding the 'pkgdb' in the list of type allowed
Fix json output
Update the help message to reflect the new group type
Merge pull request #40 from fedora-infra/pkgdb2_changes

Pkgdb2 changes