Ensure that the files property of every virtual folder returns at least an empty list and never nil.
Implemented mark folder as read.
Fix button alignment.
Group the top right buttons for consistency with the Forums.
Use labels instead of prefixing a title with a string for better discoverability.
Add date added for mission and training virtual items.
Merge branch 'lessonbin' of git://github.com/fuzzie360/coursemology.org into dev/raymoond_dev