Updated Kalman filter + smoother for DO

Still need to use Gordon’s differential equation, rather than current
difference method. Neither filter nor smoother have been tested.
temperature filter/ smoother have not been updated. Also, added
comments to metal.optim.R, and deleted kalman scripts that do not
account for gas exchange.
added comment to metal.optim about bootstrapping
Merge branch 'master' of https://github.com/GLEON/LakeMetabolizer

Conflicts:
	R/metab.optim.R