Martin Dobias 42517f8b58 [FEATURE] Mark layers as required in the project
Required layers are not allowed to be removed from the project.
This adds extra safety to protect project users from removing layers
they may think are not needed (e.g. used in joins, relations, expressions).

Users can set/unset layers that are required in project properties dialog.
2018-04-11 15:48:49 +02:00
..
2018-02-18 20:53:40 +01:00
2018-04-02 22:48:40 +02:00