Updated Moh257 arv and face page

1. In both forms, encounter date should have id="encounter-date"  (updated)
2. In both forms, encounter date should not have any default value (using #1 and #2, KenyaEMR will default the date to the current visit) (updated)
3. Moh257FacePage should have an enrollInProgram tag to enroll the patient in HIV - Added
4. In both forms, the provider field should be hidden as in MOH257 visit summary. The provider is not the person entering the form, and may not be known (done)
5. In ArvTherapy form, two elements have id="el_stage" which is an error (corrected to el_stage_ch and el_stage_ad )