new groups.html and group-controller
changes
added domain classes
layout optimizing
added groupbrowser
create, join, leave group
group combobox in entryedit
finished feature
Merge branch 'feature/Groups' into develop

Conflicts:
	src/main/java/de/hhn/labswps/wefactor/domain/Account.java
	src/main/java/de/hhn/labswps/wefactor/domain/Entry.java
	src/main/java/de/hhn/labswps/wefactor/domain/MasterEntry.java
	src/main/java/de/hhn/labswps/wefactor/domain/ProposalEntry.java
	src/main/java/de/hhn/labswps/wefactor/domain/VersionEntry.java
	src/main/resources/templates/entries.html