Collapse class button, when it was second time clicked.
When expander collapsed, all class details collapse as well.
Comments.
empty string removed.
Merge branch 'Sitrus2' into DUI-CollapseClassDetails
Method renamed. Comment added.
ClassDetailsVisibility changed.
overrideVisibility back check.
Code refactored.
overrideVisibility to hideClassDetails.
Empty string removed.
Merge pull request #61 from vmoyseenko/DUI-CollapseClassDetails

DUI: collapse class details