A few improvements to documentation for gwpy.plot

This PR fixes a couple of issues with the documentation for gwpy.plot, namely moving two useful pages out of the /docs/plotter/ path into /docs/plot/.

assigned to @duncanmmacleod

added documentation gwpy.plot + 1 deleted label

changed milestone to %0.12.0

Created by: coveralls

Coverage increased (+0.005%) to 92.247% when pulling 7ebc5426 on duncanmmacleod:plot-docs into 5174c49e on gwpy:develop.

Created by: coveralls

Coverage decreased (-0.7%) to 91.561% when pulling 7ebc5426 on duncanmmacleod:plot-docs into 5174c49e on gwpy:develop.

Merged by: duncanmmacleod at 2018-08-14 13:59:00 UTC

merged manually

closed