ImageToITK creates read accessor when output type is const

Signed-off-by: Miklos Espak <m.espak@ucl.ac.uk>
Write accessor ignores read accessors with IgnoreLock policy

Signed-off-by: Miklos Espak <m.espak@ucl.ac.uk>
ImageToItk setter for accessor options

The motivation for this is to allow setting the IgnoreLock option for reading.

Signed-off-by: Miklos Espak <m.espak@ucl.ac.uk>