Initial refactoring of domain model to include subjectgroups and allow
for greater flexibility within event groups
Added some convenience methods to compute duration and starttime etc.
Added serializable properties, so the 'old' study wizard keeps working
for now
Removed null constraints and unnecessary join tables
Implemented proper delete methods for several objects and fixed
relationship between subject and subjectgroup
Added link to samples from subjectEventgroup
Merge branch 'refactoring' of
https://github.com/PhenotypeFoundation/dbxpBase into refactoring

Conflicts:
	grails-app/domain/dbnp/studycapturing/SubjectEventGroup.groovy
Added methods to domain classes
Update toString of samplingEvent
Unintended publish of properties
getEventGroup of Sample
Merge branch 'refactoring' of https://github.com/PhenotypeFoundation/dbxpBase into refactoring
Moved getStartTimeString()
- Improved sample generation
- Bugfixes in samplingevent having starttime
Merge branch 'refactoring' of https://github.com/PhenotypeFoundation/dbxpBase.git into refactoring

Conflicts:
	grails-app/domain/dbnp/studycapturing/SamplingEvent.groovy
Bugfix for deleting subject data
Implemented getContents method for eventgroups

This is used in the frontend to show more information about an event
group.
Minor update to domain model for migration of data and multi study export
Added methods to delete eventgroups properly

Also added some loggin
Merge branch 'refactoring' of https://github.com/PhenotypeFoundation/dbxpBase.git into refactoring

Conflicts:
	grails-app/domain/dbnp/studycapturing/Study.groovy