Reference tool should have a selection dialog

[AxelRICHARD]

Currently, creating a ReferenceUsage from any graphical node in any standard diagram (General View, ...) never asks which Element should be referenced.
It should be the case, through a selection element dialog, as it already the case for many diagram tool in SysON (New Actor, New Subject...)

[jerome-obeo]

Please, assign this issue to me. Thanks.