Upgrade Wayland version to 1.7

Many tasks are currently blocked due to outdated Wayland version in CI/testing.

Ubuntu 15.04 has Wayland 1.7, while 15.10 has Wayland 1.8. Both will work fine.

Update [2]: "Linux UbuntuTouch_15_04 (gcc-armv7)" has Wayland 1.6, but that is a cross compile build. We will need an x86 platform with
Ubuntu 15.04 or later, since we want to run CI tests. (This work is ongoing)

Update [3]: OpenSUSE Leap 42.1 would be preferable to Ubuntu, since it makes sense to test Wayland on a distro where it will be used. Wayland >= 1.8 is also preferable so the protocol (wayland.xml) can be updated independently.