Global Menu Applet

Summary:
This restores the global menu applet which you can place in panel.

The applet provides two views namely Compact and Full View.
Views can be switched from applet's settings.{F859590}

* Compact View provides a single button for accessing the application's
menu
{F859505}

* Full View shows the full application menu in panel
{F859566}

See https://phabricator.kde.org/D3156

Reviewers: #plasma, broulik, chinmoyr

Subscribers: andreaska, davidedmundson, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D3706