Release 2.0.26 (#4087)

- setting "rounding days" not required
- developer: added user pref for public holiday group (to be used by plugins)
- developer: added WorkingTimeYearEvent (to be used by plugins)
- user pref: cleanup work contract form and support more fields (to be used by plugins)
- code cleanup
- bump theme and composer packages

composer.json

@@ -35,7 +35,7 @@
         "friendsofsymfony/rest-bundle": "^3.0",
         "gedmo/doctrine-extensions": "^3.6",
         "jms/serializer-bundle": "^5.0",
-        "kevinpapst/tabler-bundle": "^0.20",
+        "kevinpapst/tabler-bundle": "^0.21",
         "league/csv": "^9.4",
         "mpdf/mpdf": "^8.0",
         "nelmio/api-doc-bundle": "^4.0",