Support workspace-relative URIs in cross-resource references

[bergmanngabor]

$subject is required by EMFSplitter models.

[bergmanngabor]

I have added the following optional parameters to the offline lens command line, in order to supply information on workspace layout:

• -goldWorkspaceMapping path/to/gold/workspace-config.properties identifies the path to a ..properties file, which contains lines of the form projectName=actualProjectPath for each known and relevant project in the gold repo
• -goldRepositoryRoot /path/to/gold/repo/working/directory identifies the working directory where the gold repo is checked out, so that entries in the .properties file mentioned above can be paths relative to the repo root. This locator mechanism is provided so that (super)users do not have to know which temp folder the server-based hook will check out the repo to; they can simply use repo-relative paths that are the same for both the front and gold repo, for any machine.
• -frontWorkspaceMapping path/to/front/workspace-config.properties likewise
• -frontRepositoryRoot /path/to/front/repo/working/directory likewise