RFC: remove resources feature is missing

[Fania Bremmer]

** Proposed Change **
We need a "remove resource from current activity" feature, as Aaron 
already pointed out, in the context menu

** Reason For Change **
This "Remove resource" option should be displayed in every context menu, 
in exactly the same way, consistently for every type.

A lot o users asked for this feature, but would not have tried the 
context menu for this... any other option where to put it? Or maybe not 
repeating the whole context menu discussion and just put "remove" in the 
context menu for every resource. There should be also a "delete" to show 
the difference to the user

** Implementation Details **
- adapt context menu
- ...