Update naming and formatting of CollectedSampleController.findLastDonationForDonor (See #60)
Update 'Donor Not Due to Donate' functionality (See #60)

Was using a method call to donorRepository.findDonorById using
DonorNumber - updated to use
donorRepository.findDonorByNumber(collectedSample.getDonor().getDonorNum
ber()).
Remove extensive validation (not the right place to handle this)
Handle case of new donors (i.e. no previous donation).
Use Map<String, String> for jsonResponse, rather than Strings.
Update alert messages