add support for resource cardinality

[anb0s]

For some tools (diff, merge etc.) we need a way to provide number of selected resources e.g. [1..1], [1..3], [1..*] etc.

A command can define needed cardinality and menu can accept it

• do not show the menu if selection does not fit
• or show it if selected more and let user select wich to use

[anb0s]

related to #41