MKtl: add a "public" shortcut method for allKnown devices.
MKtl: opening a device with a different shortname, and fake if necessary.
MKtl : improve information in printing of postPossible
MKtl: rename allKnown to allDescriptions, and loadAllDescs if necessary.
MKtl: make posting about loaded device descriptions optional, and inform in verbose mode about whether or not device descriptions are actually reloaded.