Summary
Allow the display for the ColorToGrey module to show an arbitrary number of channels.
Background and rationale
Increasingly CellProfiler is used to study images that have been imaged in >3 channels; for simplicity's sake, these are often stored as a single multichannel file whose colors are split using ColorToGrey's Split->Channels mode. Split->Channels can work on images with an arbitrary number of channels to split them all out, but in this mode only displays the first 3 channels it has split out, no matter how many channels are included. This can cause confusion.
Proposal
One of two solutions would be helpful- ideally we could show every channel as it's split out, as CorrectIlluminationApply can for n-channel images. If for some reason that wasn't possible, simply adding a sentence saying "N more channels not shown".
Implementation