Summary:
This patch updated the getting started section
 - Added information about the lime ppa and other changes in installation section
 - corrected the creating new document section according to the changes in layout
 - added new interface image
 - some other minor tweaks

Reviewers: scottpetrovic, woltherav, #krita_manual

Reviewed By: woltherav, #krita_manual

Tags: #krita_manual

Differential Revision: https://phabricator.kde.org/D19630