Combination of 25 commits...

cleanup and add documentation for:
  * gof.ds
  * print.ddf.gof
  * prob.se
  * summary.ds
  * DeltaMethod
  * det.tables
  * plot.det.tables
  * plot.trial
  * plot.trail.fi
  * plot.ds
  * NCovered
  * plot_cond
  * plot.io
  * plot.io.fi
  * plot.rem
  * plot.rem.fi
  * plot_uncond
  * ddf.gof

Other stuff:
 * modernised how version and build number are reported
 * added tests for trial.fi with golf tee data
 * moved solvecov into a separate file
 * moved average.line.cond into a separate file
 * doc update
 * removed calcp and references to it, since it's no longer used
 * new "new" argument to plot.ds