Improve flexibility of size and mass distribution binning

[jcurtis2]

Explore high and low resolution binning options for the size distribution and mass distribution. Currently, there are 100 bins always. This is probably too many in the first place - we should limit it to a certain number of bins per decade of particle size.

Options:

• More flexible: allow setting of number of bins in namelist and always output all 100 bins. Downside, some of these will be unused. This is probably confusing and also results in extra output of zeros.
• More clean: allow for a two/few choices of number of bins based on number per decade in the namelist and configure WRF to only output that number. Downside, requires adding to the namelist multiple options of number of bins via the Registry.