Adding new birthtime column in person table.

Currently Openmrs does not support recording of birth time of a person. So, we are adding a new column "birthtime" of time datatype to person table.

See this OpenMRS Talk topic for discussion leading to this ticket.

• person.birthtime should be an optional (null allowed) TIME column in the database.

• Person.getBirthtime() should return a java.util.Date with the date portion set to the date from Person.getBirthdate(). If birthtime is missing (null), Person.getBirthtime() should return null.

• Person.setBirthtime(java.util.Date) should ignore the date portion, updating only person.birthtime.