Remove subsample argument from findThreshold?

[Jason Vander Heiden]

With the new subsample argument to distToNearest, and if stick with the new density threshold bandwidth detection, we probably don't need the subample argument in findThreshold.

It's also inconsistent because it doesn't apply to method="gmm".

[Jason Vander Heiden]

Moved subsample out of smoothValley and into findThreshold before either method. Also set subsample=NULL as it no longer seems necessary.