Add CommandError wrapper around CommandantError
Add CommandError wrapper around CommandantError

Works around the inability to extend generic types with protocols.

abbeycode/Carthage,erichoracek/Carthage,abbeycode/Carthage,erichoracek/Carthage,abbeycode/Carthage,erichoracek/Carthage,abbeycode/Carthage,erichoracek/Carthage