File template dialog: show config groups in same order as in config file

Summary:
The config groups were passed via a QHash, which randomized the order
and prevents to define it by the options config file, as one would expect.

Reviewers: mwolff, KDevelop

Reviewed By: mwolff, KDevelop

Subscribers: mwolff, kdevelop-devel

Differential Revision: https://phabricator.kde.org/D4412