* Adding ChannelMemberHistory table records when DM channels are created. This ensures that both participants in a DM are shown in compliance export, even if only one of them typed anything
* Direct/Group Message channels now get pretty display names for the purpose of compliance exports
* Fixed string formatting in t.Fatal calls
* Changed uses of ChannelMemberHistory over to ChannelMemberHistoryResult in tests. This should have been done as a part of the work in XYZ-110, but seems to have been missed in this branch for some reason