[FEATURE] Integrate preliminary PackageManager API

The Package Manager from Flow has been backported and integrated as
CMS Package Manager. This enables us to use full vendor namespaces for
extensions and brings us closer to a unified TYPO3 package format.

For more Details see: http://wiki.typo3.org/Blueprints/Packagemanager

Resolves: #47018
Releases: 6.2
Change-Id: I52abedaf470cebddb3553e37581021bf368380e6
[TASK] Change travis build environment to fork

Change-Id: I6537ed9bbc6c31293044cdfe061c7478f3a1fcc5