paths cleanup:
- don't store explicit static path, but allow it to be set in the insert
- store host_prefix, which is either server name or empty
- for archival mode, absolute_paths settings controls if using absolute paths,
- for proxy always use absolute_paths
- default static path is: /static/default/
- allow extension apps to provide custom /static/X/ path

Route overriding:
- ability to set Route class
- custom init method

Archival Relative Redirect:
- if starting with timestamp, drop timestamp and assume host-relative path

Integration Tests:
- test proxy mode by using REQUEST_URI
- test archival relative redirect!