* Update travis to use ubuntu 16.04 (xenial)
Update travis to use ubuntu 16.04 (xenial) instead of 14.04 (trusty)
* add xvfb as a service to xenial distribution
* removed explicit start of xvfb
after adding the xvfb as a service, there is no reason to explicitly start it at "before_install"
* install libGL during before_install
* install libgl1-mesa-dev during "before_install"
After some changes from the Qt installers (? maybe), all Travis Android builds are not able to be configured in order to run.
Deactivating thier build till it get fixed.