think i've worked out the problem

The problem *appears* to have resulted from the last few lines of `SuomiNPPSuomiNPPDataSource.setup()`: the `setProperties(properties)` call was overwriting the data source properties that had been set earlier in the method. I opted to simply merge `properties` with the existing map returned by `getProperties()`. My limited tests resulted in `properties` always being empty.

I made things a little more flexible by (ab)using the data choice properties in `doMakeDataChoices`. This allows the `DisplayControlImpl` code in `addLabelMacros` and `getMacroNames` to check for the presence of the `granulecount` property without having to use instanceof checks and whatnot.

Things seem to work, but I haven't tested the changes thoroughly, and the code is pretty messy (I'm getting tired)…so merging this pull request is probably not a great idea. I mostly wanted to get the code online and viewable in a side-by-side diff.

(there are two buttons to the right of the "Showing 2 changed files ..." line below, "Unified" and "Split". Pick "Split" to get the side-by-side diffs)