ColorTip:
Draw the border around the color tooltip properly.

MiniProjectTargetSelector:
Fixing a few misplaced outlines

FancyActionBar:
Fixing a few misplaced outlines, also:
- deduplicate hover gradient painting code
- use pixmapcache for the hover gradient
- only draw the hover gradient if the tab is hovered
- use 0-255 as range for fading value

QtQuick Designer:
HighDPI form editor icons, and removing some since a
while unused icons.

ProjectExplorer Mode:
HighDPI graphics and fixing a few misplaced outlines

Task-number: QTCREATORBUG-15222
Change-Id: I4fcf515014317791499ad89bf6ef88d961e4b752
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>