Group option at layouts

[yhilg]

When creating layouts, it would be very useful if we could also pre-assign terminals in a group.

Example:

1. spawn 9 different instances of all shapes, tag each 3 into a different group;
2. single right click -> preferences -> layouts -> test123 -> save
3. layouts -> test123 -> profile/custom command/working directory/group name
4. beer

Using 2.14 it is currently not possible to do so.

xo