Clean up som code

[tengstrand]

Prepare the implementation of issue #431 (support for multiple workspaces) by improving the code:

• merge the workspace-clj component into workspace. Centralize how to read workspaces, and make sure it can read a workspace from both file and disk.
• normalize paths, so that e.g. "somecode/project/.." will be evaluated to "somecode".
• create examples/workspaces/backend example workspace.