Change role dialog: Combo instead of text input and better title

[skyper]

This is a follow-up of #16255. Thanks for the nice dialog

I have two enhancement requests:

1. Please, instead of Input use Change role or Change role? and Change roles or Change roles? as title of the dialog, see Change Value.
2. Use a combo input box instead of a text box similar to "Change Value" in order to:
   • offer possible values
   • show the different existing values if multiple are present .

Thank you.

BTW: skyper on #16255 comment 10:

Is it possible to include a help button and context-sensitive help anchors, please, see #18651. I plan to document this new dialog and need a name for the new page wiki:/Help/Dialog/ChangeRole or similar?

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-06-29 17:21:45 +0200 (Mon, 29 Jun 2020)
Revision:16729
Build-Date:2020-06-30 01:30:49
URL:https://josm.openstreetmap.de/svn/trunk