small bugfixes (#2655)

* improve report visibility
* fix timesheet duration, which breaks validation
* added contributing section in README
* do not allow to change project for existing activities - fixes #2576
* bump theme version to fix FOSUserBundle dependency
* use entity color instead of inherited one - fixes #2200

composer.json

@@ -29,7 +29,7 @@
         "handcraftedinthealps/rest-routing-bundle": "^1.0",
         "jms/metadata": "^2.0",
         "jms/serializer-bundle": "^3.9",
-        "kevinpapst/adminlte-bundle": "dev-master",
+        "kevinpapst/adminlte-bundle": "^3.5",
         "league/csv": "^9.4",
         "league/html-to-markdown": "^5.0",
         "mpdf/mpdf": "^8.0",