Update License to AGPLv3

[MrThaler]

Current Situation

The plugins are under the License "Apache License Version 2.0".

Issue

One of the included dependencies of this project is "org.artifactory:artifactory-api:5.4.4".
This dependency is licensed under AGPLv3. This is incompatible to being included in Apache License Version 2.0.

Solution

It seems to me the plugins should also be licensed under AGPLv3 to solve this problem.