Erroneous RegEx pattern in URLUtil #358

URNUtil uses this pattern: ^file:///\\p{Alpha}|.*$
Judging from TestURLUtil, this is supposed to detect prefixes like file:///C|. The problem is, that the pattern always matches, because | is a special RegEx character for "alternation" - and every string ends with .*.

So the backslash should probably be escaped. I'll provide a PR with a unit test that shows the issue.