Support translations defined in messages.properties

In the contrib-uicommons project, a new angular module "openmrs-translate" is defined for localization.

However, this new module only uses new message key/value pairs defined via a "message_*.json" file.

We'd like this new module to also have all the existing key/value pairs defined in messages.properties files to be able to it.

A couple possible approaches:

• Have a custom loader that can RESTful load translations
• Bundle in all the messages.properties (pulled from Transifex?) during compile time

For the first option, we may be able to use existing functionality added to uicommons:

https://github.com/openmrs/openmrs-module-uicommons/blob/master/omod/src/main/java/org/openmrs/module/uicommons/fragment/controller/MessagesFragmentController.java

Example usage here:

https://github.com/PIH/openmrs-module-pihcore/blob/master/omod/src/main/webapp/resources/scripts/visit/visit.js#L33

Discussion here:

https://talk.openmrs.org/t/translate-dashboard-widgets/11215

fyi cioan darius raff