HSEARCH-1326  Checkstyle Improvement

https://hibernate.atlassian.net/browse/HSEARCH-1326

To check that in the code there aren't two consecutive spaces I've decided to create a checkstyle rule. I couldn't do it with regexp because  in some test we have String containing multiple spaces and as far as I know the is no way to tell to the existing checkstyle rule to skip strings.

The creation of a checkstyle rule requires a Java project so I've decided to mov checkstyle in it's own module. This mode seems to work better with eclipse (but it might be my eclipse configuration that it is messed up) but it also give us the opportunity to move the checkstyle rules to an external project that could be shared. I would like to use the same file in OGM for example.