Defined the content type name for Play Template files

Fix #62
Merge pull request #63 from dotta/issue/no-content-type-for-play-template-file-62

Defined the content type name for Play Template files
Updated scm config in POM required to extract the GH hash
wip
Automatically add Scala nature when opening Play2 Template editor

Java Play2 Template project don't have the Scala nature by default, and this
caused an exception to be thrown whenever the user tried to open a Play2
Template editor because the editor needs access to the ``ScalaProject``
facilities.

The implemented solution is to automatically add the Scala nature if a project
doesn't have it.

Fix #33
Minor clean-up in code and POM

* Removed unused import in ``RouteTestSuite``.
* Added explicit return type on public methods.
* Remove comment in POM about Play 2.0.x support.