Update DatumGregCal
Merge branch 'master' of https://github.com/MaximeRyckmans/JavaOefeningen.git
Update DatumGregCal
Created Child classes for Opdracht and Interface Valideerbaar
motherfuckeeeeeeers. Makziem out!
Merge branch 'master' of https://github.com/MaximeRyckmans/JavaOefeningen.git
Added some helpful methods like equals and hashcode. Made a testmethod
for OpdrachtCatalogus.
Added some stuff like comparable and iterable interfaces.