Add basic pology posieve request support

Summary:
Configuration dialog

I've added an option to posieve.py previously to allow a launch on a single entry. This is just a start, the goal is to have a better integration of Lokalize as a retriever of pology information and not only as a client for pology.

Reviewers: Localization, aacid, ltoscano, mlaurent

Subscribers: Localization

Differential Revision: https://phabricator.kde.org/D15181