Summary:
some optimizations for tablet mode (touch first, but also on
transformable laptops flipped to tablet)
and some for specifically the mobile case (mobile phone)

* hide the top toolbar in phone mode
* in tablet mode (and therefore on phone mode too) don't select text but drag the item laterally to dismiss it

Test Plan:
* on phone form factor for the new behavior
* on touch laptop in tablet mode
* on desktop for its behavior not changing at all

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: nicolasfella, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D24765