Move currencies locale to sub folder.

Having it in locale dir create failure and missbehaivour for locale
specs and localeapp pull and push. It do not seems DRY because this
conversion should be controlled by rails_i18n.
Append routes.
Fixes engine issues.

- Move all dependencies to gemspec.
- Add missing assets support.
- Fix bug with version in gemspec.
- Fix error with MultiCurrency module.