Add option to easily configure and start a hotspot

Summary:
This adds a simple checkbox, which will create and stop hotspot. Hotspot can be also
configured from the KCM, where users can choose a name and password.

BUG:  413323

{F7857835}

Reviewers: #plasma, ngraham, #vdg, apol

Reviewed By: #vdg, apol

Subscribers: meven, cblack, alexde, mthw, apol, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26392