fixed error messaging on violating MUST_EXIST flag if Patient does not
exist (before error message incorrectly stated: was violating
MUST_NOT_EXIST flag)

if Patient not found, check if it could be because of mismatch in
birthDate by just matching on first and last name. If that matches flag
an error rather than considering the Patient not found because in most
cases it correctly indicates that there is an error in the birthDate
either in the data file or the LAVA database