Fixed T29550 - load save label presets

Summary:
+ refactored the save/load code into the module

Fixes T29550.

Test Plan: code review; application test (saving and loading presets should work now)

Reviewers: O1 MITK Reviewer Group I, kislinsk

Reviewed By: O1 MITK Reviewer Group I, kislinsk

Subscribers: kislinsk

Maniphest Tasks: T29550

Differential Revision: https://phabricator.mitk.org/D814