support budgie panel transparency

[danielpinto8zz6]

This adds support for the budgie panel dynamic / full transparency option

[hrdwrrsk]

seems 'out of rule', I need panel transparency that compatible with some wallpapers, not full panel transparency (40% or 50% opacity is good)

or add shadows in text and icons for easier visibility like elementary's wingpanel

[danielpinto8zz6]

humm okay, I did like the default theme of budgie, since this is a setting you can allways have it default

[hrdwrrsk]

merged, but totally untested. I should install Ubuntu 18.04 minimal install + Budgie from ubuntu-budgie/backports ppa to test it soon :\

[danielpinto8zz6]

Check it: https://streamable.com/424q3

[hrdwrrsk]

known problems:

• with some wallpapers, running app indicator is hard to see