This PR continues the work started in PR #8951.
This commit replaces occurences of #include "qgis.h" by #include "qgis_sip.h",
where possible = when files only depends on SIP_XXX features.
Translated objects and tests included:
- [x] layer names
- [x] layer group names
- [x] relation names
- [x] attribute alias (if no alias, then the field translation)
- [x] forms group box titles
- [x] forms sub group box titles
included restructured with QTranslator object.
Updated test-data used for the test.