[Development] Enginio version and branch names

[Frederik Gladhorn]

Hello all,

To make dealing with Enginio a bit easier (I get asked for the right version 
number for each release and keep being confused myself since it doesn't see 
much activity), I will change the future branch names and version number.

As you know we cannot change the major version as that is not binary 
compatible, so the major .so version will stay at 1. But we can align the rest 
of the version to Qt release versions.

Branches:
follow Qt branches: 5.6, 5.6.0, etc

Version numbers:
follow Qt in minor and patch: 1.6.0 will be released with Qt 5.6.0.

Cheers,
Frederik