[libinput] Add support for clickfinger and button areas click method

Summary:
Added support for libinput clickfinger , areas method for touchpad KCM
Also added mock methods.

Included commits in branch libinputClickMethod:

         Added libinput mock methods
         Added : 1. setScrollMethod 2. added key value pair in QMap 3. added methods for Q_Props
         Added Q_Props for click method, signal
         Added variables and initialize in constructor

Reviewers: #kwin, graesslin, davidedmundson, zzag

Reviewed By: #kwin, graesslin, zzag

Subscribers: zzag, graesslin, davidedmundson, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D17577