JerseyUriBuilder: allow template parameter regexes to contain braces

[cky]

The template parameter syntax allows the regex to have one level of braces, as long as they are evenly matched, arbitrarily many times.

However, JerseyUriBuilder does not currently handle this correctly: all the non-URL-safe characters (such as backslashes) after the first closing brace gets encoded, making the regex unable to be compiled successfully.