New plugin to read Kontron IMG files

Request to support Alan Boyde's Kontron BSE capture from the Zeiss DSM
962 SEM.
Kontron IMG: working version
Kontron IMG: add licence and a little documentation
Kontron IMG: use all six magic bytes for file identification
Kontron IMG: set FileInfo
Merge branch 'io' into testing
Particles: optionally report ellipsoid axis unit vectors