Allow addl plot args

[lindsayplatt]

Now plotEGRET("fluxBiasMulti", lamprey_nitrate, estdat, preds, meta, moreTitle="LINEAR") won't produce an error about multiple actual arguments. See #107

[wdwatkins]

👍

[aappling-usgs]

Looks good! While we're doing this, I wanted to revive a request I made in #138 : "can we take out the flow normalized concentrations with plotFlowNorm=FALSE?" - this would be very similar to what you just did for moreTitle=NULL, and I think it makes sense for the same reason moreTitle does.

Would also like to suggest that the default for moreTitle be 'loadflex' rather than NULL. It's not very descriptive, but it will look better out of the box than NULL.

[coveralls]

Coverage remained the same at 48.15% when pulling ebb8f6a on lindsaycarr:allow-addl-plot-args into 346c2ee on USGS-R:master.

[aappling-usgs]

Thanks! 👍

[coveralls]

Coverage remained the same at 48.15% when pulling 26d3a42 on lindsaycarr:allow-addl-plot-args into 346c2ee on USGS-R:master.