Javadoc fixes for JDK 8

I've fixed many Javadoc problems, but now the build fails at the "Querydsl - Maven plugin" module com.mysema.query.maven.CompileMojoTest:

```
src\test\java\com\mysema\query\maven\CompileMojoTest.java:5: error: package org.apache.maven.project does not exist
import org.apache.maven.project.MavenProject;
[...]
```

I'm not sure how to proceed.