Prevent %2F (forward slash) in path component of URIs

Path variables are currently encoded such that forward slashes become %2F. This is disallowed by Apache unless the [AllowEncodedSlashes](http://httpd.apache.org/docs/2.2/mod/core.html#allowencodedslashes) directive is specifically enabled.

Encoding forward slashes to %252F (i.e., double encoding the percent sign portion of %2F) allows the generated URI to work properly with Apache without enabling AllowEncodedSlashes.