URL Field - pure Angular directive and l18n values

- Modified dtv-url-field.js to now be a pure Angular directive and not wrap the jQuery plugin
- Added URL Field HTML template for Angular cache
- Updated en translation.json with URL Field values
- Removed an e2e test that checked for default value, now using a placeholder value instead
Merge pull request #65 from stulees/feature/url-field-pure-ng

URL Field - pure Angular directive and l18n values