Path, url and subdir cleanup & test

issue #1754

- remove path (it was only used once, and not needed)
- change webroot to subdir
- add unit tests for config.paths
- various other cleanup
- renamed client-side ghostRoot to subdir
- added url helper for client
Merge pull request #1764 from ErisDS/path-cleanup

Path, url and subdir cleanup & test
Shared folder asset handling

fixes #1659, fixes #1668

- removed relative asset url from css
- added asset helper to client
- updated references to shared assets
- added functional tests