support to watch multiple class folders in maven multi module project

Hey guys, I added support to enable ninjs superdev mode for maven multi module projects with quite minimal changes. If maven project contains modules they are picked up via maven session projects / reactor projects. If not everything works as it was designed before. 

We plan to use this feature with the following simplified maven multi module project:

parent-project
 - module-a
 - module-b
 - module-c

You may call mvn ninja:run on parent-project to enable superdev mode for all modules contained.
These code lines do 
 - check if currently handled maven project has modules declared
 - search for module projects in maven session / reactor (all projects build by maven). This is needed due to maven API providing module names only an not MavenProject instances