MT: Translate with context

The descriptor "Corolla Color" in en is translated to "Corolla Color" in es. This probably has to do with capitalization and brand names.

Testing shows that by using a translation context "Corolla Color is the name of a crop descriptor." the MT will generate a correct translation: "Color de la corola".

In this ticket we add context templates to content/language.properties for each entity with MT support. For Descriptor the templates are:

translate.context.Descriptor.title={0} is the name of a crop descriptor.
# translate.context.Descriptor.description=It is further defined as: {0} # Unsure about this
translate.context.Descriptor.codes=Valid options are {0}.

The machineTranslate() method will generate a context string by populating these "templates" and pass it to the machine translation service.

If a descriptor has codes, we can concatenate their titles into (for example) "Valid options are Red, Green, Blue".