#58 Check for duplicate UIDs

[Arnout Engelen]

Makes the validation step of a Calendar check if multiple components with the same UID are present.

Unit test also supplied. This validation rule made 3 ics files in the old 'valid' set fail. AFAICS these files are actually wrong, so I moved them to the 'invalid/supported' set.

http://repo.or.cz/w/ical4j.git/commitdiff/a7e0f6ea6ade185347c40c2546b328263ae84713