Fix NullPointer during multi-threaded builds

[terje2001]

When I do multi-threaded builds (mvn install -T4), I get the following NullPointer:

Caused by: java.lang.NullPointerException
    at me.qoomon.maven.GAV.of (GAV.java:74)
    at me.qoomon.maven.extension.gitversioning.VersioningPomReplacementMojo.execute (VersioningPomReplacementMojo.java:50)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:134)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:208)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:200)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:196)
    at java.util.concurrent.FutureTask.run (FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:511)
    at java.util.concurrent.FutureTask.run (FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:624)
    at java.lang.Thread.run[INFO] 

This PR fixes that by letting Maven inject the right MavenProject object rather than trying to fetch it from the MavenSession object.

[qoomon]

Thanks a lot. I will release a new version ASAP.

[qoomon]

@terje2001 do you know if it's possible to get dependencies within me.qoomon.maven.extension.gitversioning.VersioningModelProcessor vie @Parameter as well?

[qoomon]

just released version 3.0.1

[terje2001]

Sorry, do not know Mojo API well enough to comment on '@parameter' and its usage.

Thanks for accepting the PR and releasing it. Appreciated!