tweak fill color logic
prevent some conf variables that don't make sense for BaseCoverage from affecting it
include "Total" in BaseCoverage score display
added a NestedFrequencyTable class to use for keeping track of counts for nested categories
bugfix to BAM store error handling
add some comments to NestedFrequencyTable, add a categories method
extract WiggleBase calculation of per-pixel displayed scores into a separate method
make the coverage scores in BaseCoverage be NestedFrequencyTables, use that to provide info on which strands contribute to specific SNP counts