jarpackager integration notice - incompatible change

Hi,
in order to reduce the number of classes in JarPackager's apis, it was 
identified that the following three classes can be dropped without a 
major loss of correctness or expressivity:

SourceContent, ResourceContent, BuildTargetContent

Only their common predecessor -- DescriptorContent -- will remain there.
Though it allows a ClassCastException to occurr within jarpackager if 
somebody feeds in something different from Source/Resouce/BuildTarget 
Descriptor, the error is detected soon.

All impacted modules on the prj40_prototype build have already been 
corrected. If your code is not on the build and uses any of the above 
classes, it will not compile after the reduced version is checked in. To 
fix that, any usage of the three above classes from JarPackager's apis 
must be removed as follows:
use DescriptorContent instead
use DescriptorContent.create(.) instead of direct constructor

Thus corrected code will work with the current version. If there are no 
objections, the new version will be committed tomorrow late afternoon.

Thanks,
-Ondra