www/piwik: Update from 3.2.1 to 3.4.0

Changelogs:

• https://matomo.org/changelog/matomo-3-3-0/
• https://matomo.org/changelog/matomo-3-4-0/

Also:

• Rename the port to match renaming of the project itself
• Flavorize port

Reported by: Nicola Tiling <nti@w4w.net>
Reviewed by: Nicola Tiling <nti@w4w.net>