Add extreme metrics
Improvements to graphics2

* Added -C <clim> (divides instead of subtracts climatology)
* Added -m {minobs,maxobs,minfcst,maxfcst} (Outputs min/max across all non-x-axis dimensions)
* Enable -type map
* Enable -fs (figure size)
* Enable -nomargin
* Only draw connecting line if x-axis is continuous (e.g. date, offset)
* Bug fix in qq, scatter, cond (bug introduced with timeseries)