Fix static directory mounting
Allow index page to be specified when mounting static dirs
Allow static dirs to have multi-segment prefixes

In other words, you can now mount a static directory with a prefix
like 'docs/xyz' or 'docs/x/y/z', etc.
Add Resource.path()
Don't set request.resource_method

This is unnecessary because we can just use `request.method` to get at
the resource method.