Fixing #1557 - Environments are now in REST URIs

This commit includes multiple, related changes, all
in one commit because the whole thing was necessary to
reach a functional tree again:

• The URI starts with the environment, so: /production/certificate/foo /development/file_content/path/to/your/file
• All REST handling is done by a single instance mounted at / for webrick and Mongrel, rather than having individual instances mounted at, say, /certificate.
• All REST URI translation is done by an API module. Currently only the 'v1' module exists with no support for additional modules, but it's well-separated and will be easy to expand as we need it.

Signed-off-by: Luke Kanies <luke@madstop.com>