Initial version of budgie-restart-applet

Summary:
Inclusions of Budgie Restart Applet in the repository. Fixes T5047.

Signed-off-by: Pierre-Yves <pyu@riseup.net>

Test Plan:

• Install Applet
• Restart session
• Add applet to panel
• Restart Panel, WM and desktop.

Reviewers: Triage Team, JoshStrobl

Reviewed By: Triage Team, JoshStrobl

Subscribers: JoshStrobl

Maniphest Tasks: T5047

Differential Revision: https://dev.solus-project.com/D3107