Migration of GSAK filters

[nagisml]

Problem Statement

GSAK filters should be migrated as good as possible into OSAK
Filter features which can not be migrated will be added as SQL comments to the WHERE clause

These will support finding missing filter features

Proposed Solution

Create GUI based GSAK Filter import/migration as available for GSAK databases.

A alpha version is available based on 1.19 here https://github.com/nagisml/OpenSAK/tree/feature/migrate-gsak-filters

[nagisml]

result based on my test filters

[nagisml]

@AgreeDK pls assign

[AgreeDK]

Implemented in #935 and shipped in v1.21.0-beta.1: File → Import GSAK Filters… reads the saved filters from your GSAK database (gsak.db3 or a GSAK backup .zip) and turns them into OpenSAK filter profiles. Criteria OpenSAK can't express yet are kept as comments on the Where tab, exactly as proposed here, so they also show us which filter features are still missing.

Thanks @nagisml for both the idea and the implementation!