Add standard pen widths and replace hardcoded numbers

Summary:
The replaced numbers are directly related to the width of the pen.
This patch likely doesn't replace all of the numbers that could be replaced.
It just replaces the ones I'm currently certain of being related to pen width.
The goal is to make the code show the intent of the designer.

Reviewers: #breeze, #plasma, hpereiradacosta, ngraham

Reviewed By: #breeze, hpereiradacosta, ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26217