Switch from Ionic.Zip to SharpCompress to be able to handle other
types of files (.RAR, etc).
Test that correct exception is thrown when trying to read a file which
doesn't exist in a collection.
Rename ZipCollection -> CompressedFileCollection.
Replace "zip" with "compressed file".
Make "Type" column in message log form longer to support "compressed file"
instead of "zip".
Replace "zip" with "compressed file".