[Dltk-dev] fix for resetting debug engine preferences

["Jae Gangemi" <jgangemi@xxxxxxxxx>]

hello all -

  it looks like restoring the default values for debugging engines and the likes is currently broken. i have a fix for this, but it required me to add a new method to the DLTKContributionExtensionManager class so i can retrieve a contribution based solely on its configured priority in the plugin.xml. otherwise, if an id based IDLTKContributionSelector is in use, it will continue to use whatever the last saved value is. 

  with the 1.0 ramp down policy in effect, i'm guessing that this change is prohibitted by the api freeze, so i wanted to see how to proceed.

  i've attached a patch so others can take a look.

  this patch also included a fix to automatically selected whatever the default global interpreter is, rather then the making the user explicitly pick one, but that is entirely an internal change.

-- 
-jae