graphics/qgis: Update to 2.18.17

Additional port changes:

• Added PYUIC_PROGRAM because cmake couldn't find pyuic4
• Flavorized some dependencies with missing flavors
• Silenced/improved some commands
• Updated WWW

PR: 226190
Submitted by: Rainer Hurling <rhurlin@gwdg.de> (maintainer)
Approved by: tcberner (mentor, implicit)