Improve collapse functionality, and improve various collapsed states' styles

Moderation message now oneline, with flag icons accordingly
Collapse now triggers flow-topic-collapsed and flow-topic-expanded
Removes excess padding at end of topic summary
Adds flag and styling to moderation message
Changes moderation state background colors (white for closed/deleted, grey for hidden)

Change-Id: I537fdd26c960d713538b3ecd126d735b3a5db2df
Merge "Improve collapse functionality, and improve various collapsed states' styles"