Patch available to make .classpath entries portable - relative to ECLIPSE_HOME

This patch modifies the DerbyUtils class to add variable entries relative to ECLIPSE_HOME as described in the comments below, so that eclipse projects with Derby Nature can be committed to an SCM without causing build path errors. I did not think any of the derby functional tests were applicable to this ui action, so I manually tested the code by trying the following:
1) Adding Derby Nature to a java project
2) Starting and stopping a database with the derby nature
3) Removing the Derby Nature from a java project

The code modification is only required on the add and not on the remove since the current remove looks for any entry that ends with the correct JAR names.