Allow plugins/extensions to request specific positions in menus, choose order of commands, layout of dialogs

[matterhorn103]

Currently anything added to a menu or dialog by a plugin seems to be displayed in alphabetical order. Ideally the plugin could choose how these things are displayed.

If I understand correctly, in the code, menu options are given an integer as a sort of "priority" and are ordered by that, and dividers are added every 100. So ideally what would be implemented:

1. When a script specifies its location using --menu-path, it would be able to provide a number to use for sorting at each level so that it could affect both the plugin's location in the menus, but also the relative order of the plugin's commands if it has multiple.

Secondly, the options for customizing script-specific dialogs are fantastic and allow for a lot of flexibility, but the way things are displayed is not controllable:

2. The relative order of dialog widgets specified in "userOptions" should be settable.

I am not sure what the mechanism is for the latter in other dialogs in the program.

[ghutchis]

Adding "menu priority" wouldn't be too hard. Maybe there's a way to add it to --menu-path, like:

"Build|Insert{32}" to indicate the priority.

I guess you also want to add an "order" attribute to change the sort of the "userOptions"? Makes sense.

[matterhorn103]

Exactly that would be perfect :)

[ghutchis]

See #1501

I'll have to do some work on the "order" attribute.

[github-actions]

Here are the build results
Avogadro2.AppImage
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[matterhorn103]

Remind me to add stuff to the docs about this before you close the issue!

[github-actions]

Here are the build results
Avogadro2.AppImage
macOS.dmg
Win64.exe
Artifacts will only be retained for 90 days.