Fifth revision of the konq sidebar code.

Summary:
Brings back the konqueror sidebar panel, with a few new features. Buttons for: home, root, fonts, bookmarks, places, settings, remote, and others.
Automatically detects and selects in the panel the current location of the active view (except for the places panel, for now).

Test Plan:
Press F9 to bring up the panel. Try multiple combinations of:
 having split window views
 toggling the panel on and off
 toggling the panel visibility on and off
 clicking on items in the panel listings
 navigating using the locationbar, history, or clicking inside the view itself
 selecting different active view, including those with loaded urls that match and don't match the panel button

Reviewers: dfaure

Reviewed By: dfaure

Differential Revision: https://phabricator.kde.org/D28527