Probe type appropriate for DAPI

[saskiad]

this is a stain that binds to DNA. Our current models don't quite work. Still need to figure out the right approach.

[dbirman]

• NucleicAcidProbe is a possible solution here, in the DiscriminatedList for FluorescentStain
• Need descriptions to really clearly communicate GeneProbe vs NucleicAcidProbe
• FluorophoreType may need a "ProbeFluorophore" option to indicate the fluorophore is the same as the probe