Identify - UI element (button?)

[phated]

Add UI element (possibly a button) to display the Identify dialog (if not already displayed) and performs the Identification process on all available ports, showing the results in the dialog.

Split out from #128

[urbantumbleweed]

I labelled this as a UX issue because we need to know when and how the UI element representing the 'identify' functionality will be presented to the user.

[PropGit]

This relates to issue #81 and possibly issue #92.