Improve Readability of Irida Next-Facing Descriptions

[emarinier]

We could use better descriptions for these:

For example:

--pd_distm: The distance method/unit, either hamming or scaled. For hamming distances, the distance values will be a non-negative integer. For scaled distances, the distance values are between 0.0 and 100.0.

Try to include better descriptions, bounds, more detail about what these parameters effect, etc.