[addons] separate out Broken and Unmet dependencies in the UI
[addons] don't prompt for uninstall without first checking the add-on can be done (2 dialogs not required)
[addons] prompt if an add-on is used by another and the user attempts to disable it.
[addons] fix: only prompt if the add-on is a compulsory dependency on uninstall/disable
[addons] cleanup CStdString usage
Merge pull request #3602 from jmarshallnz/broken_vs_deps

[addons] various fixes/improvements