Added --show-variant-samples option to gemini_query

This which adds a column to the output listing all
samples containing a variant (HET or HOM_REF).
Added total, het and hom_alt columns to --show-variant-samples.
Added --sumarize option to stats.

--summarize plus a query will summarize the amount of het
and hom_alt variants each samples has returned by the query.
Added slightly less awful naming.
Added documentation for --show-samples and --summarize.
Formatting fix.
Formatting fix.
Merge pull request #147 from roryk/master

Added optional column of which samples have a variant to queries.