Allow user to choose (No Topic)
Paint checkmarks on dropdown menus in Linux (BL-509)

On Windows, we use a custom renderer to prevent an errant white line,
but on Linux, this renderer prevents the checkmarks from painting.
Remove IDisposable from NaturalSortComparer

There is no reason that NaturalSortComparer should implement
IDisposable - it doesn't deal with unamanged objects or other
objects implement IDisposable. Having it derive from IDisposable
requires us to call the Dispose() method if we want to follow
best practices.
Merge pull request #76 from andrew-polk/BL509_ShowChecksLinux

Paint checkmarks on dropdown menus in Linux (BL-509)
Merge pull request #75 from gmartin7/BL-644AllowNoTopic

Allow user to choose (No Topic)
Merge pull request #77 from ermshiperete/IDisposable

Remove IDisposable from NaturalSortComparer