adding luganda translations of the error messages for the iavi study. updating the tree app to do its tranlations on the whole error string rather than the individual answer terms.
adding luganda translations of the error messages for the iavi study.
updating the tree app to do its tranlations on the whole error string
rather than the individual answer terms.

unit tests for these translations

eHealthAfrica/rapidsms-decisiontree-app,ehealthafrica-ci/rapidsms-decisiontree-app,ehealthafrica-ci/rapidsms-decisiontree-app,caktus/rapidsms-decisiontree-app,eHealthAfrica/rapidsms-decisiontree-app,caktus/rapidsms-decisiontree-app,caktus/rapidsms-decisiontree-app