XD-1831 Code review fixes + polishing

* Admin UI - support Unicode RegEx
* Add XRegExp library (For Unicode support)
* Add support to match both `password` and `passwd` parameters
* Fix `JobsController#list()`
* Fix JavaDoc in `StreamUtilsTests
* Add one more test to `StreamUtilsTests
* Add `toString()` to `org.springframework.xd.module.options.type.Password`
* Add tests for `org.springframework.xd.module.options.type.Password`
* Add more tests to `directives.js`