undo some of the changes due to klutometis/roxygen#127
fix: use height_cm instead of width_cm
New themes panel.margin.x and panel.margin.y

Fixes #839
Update .Rd file
undo bogus
Merge branch 'facet-headers-enh' into develop
Merge branch 'feature/839-facet-margin' into develop

Conflicts:
	NEWS
	R/facet-grid-.r