Dialects scanning added

Hi Emanuel !

Here is my modest contribution :-)

Some important notes :

 * I didn't break the loading of existing XML files, a new method is just called inside start(BundleContext context) to load other dialects, until "legacy" XML files exist in their respective original JAR
 * I think the scanning should be improved (the time increases by the amount of project's dependencies)
 * At the moment, the plugin does not differentiate attribute and element processors but I think it shouldn't be difficult to add this new behaviour 

I need to run some other tests to see if dialect definitions are also scanned inside the current project's resources and not only inside the project's dependencies.
It could allow to live test dialect development ! :-)

Some useless notes :

 * It's quite impressive how Eclipse handles the plugin development ! A real war machine ! :-)
 * The same for IntelliJ would be great, do you want to take a stab ? ;-)