first stab at implementing trimmed mean coverage
trimmed mean coverage appears accessible from cmdline, other assorted changes
Added in all but one of the extra coverage calculators / estimators
Now to merge Bens changes
Merge branch 'trimmed_mean_coverage' of github.com:wwood/BamM into HEAD

Made sure Ben's changes meshed correctly. Looks good now.

Conflicts:
	c/coverageEstimators.c
	c/coverageEstimators.h
	c/test.c