Fixes #239 (No error when a poorly formatted RegEx is used with tag_rule)

The changes in this PR catch errors in the format of the regular expression value passed in when creating a tag matcher with a 'like' comparison method (by creating a new Regexp using the string value that is passed in as part of the RESTful services request catching any errors that might be thrown during that process, then returning a sensible error back to the user). This should resolve the bug described in issue #239 (where the error was only detected when the tag matcher was used, not when the tag matcher was created (and added to a tag).