Methcounts format for array data

[andrewdavidsmith]

Ideally the methcounts format for array data should be as uniform with the ordinary methcounts output as possible. I think this means using a numerical value for reads and methylation level. I propose here to use 0 coverage for no value, and 1 coverage for some value, while a 0.0 level would be required for 0 coverage. This seems consistent with the use in the pmd program. Fixing this requires changes to the docs and to the pmd program source.