Improve usability of Manage Custom Menus dialog

[Martyn Gigg]

The current version of the 'Manage Custom Menus dialog' is confusing to use. It needs to be update to be based off a form that can more easily be edited. Also replace the +/- buttons with something more descriptive.

[Michael Whitty]

(In [5797]) re #1504 - changing the Manage Custom Menus interface to one based off a QtDesigner dialog.

[Michael Whitty]

(In [5828]) re #1504 - tidying of ManageCustomMenus code, addition of doxy comments, adding ToolTips to ui file

[Nick Draper]

fill in missing resolution

[Janik Zikovsky]

(In [5953]) Refs #1504: made the dialog box messages more helpful.

[Janik Zikovsky]

When I first ran into this dialog in its current form, I was still very confused as to how to run it. I have clarified the messages, which should help, but I think it could still use some work. Perhaps the list of scripts should be auto-populated when opening the form? It makes little sense to add a script on the left just to pop it in the right.

That said, I am passing the ticket for this iteration; there is documentation so it is possible to use. Perhaps this can be worked on later.

[Stuart Campbell]

This ticket has been transferred to github issue ​2351