gmtlogo/psbasemap: Ensure the long options for -D are consistent with other modules

[seisman]

Some GMT modules like image/logo/legend/colorbar can add embellishments. These modules have similar syntax for placing these embellishments. For example, logo's -D option has the following syntax:

-D[g|j|J|n|x]refpoint[+hheight|+wwidth][+jjustify][+odx[/dy]]

in which [g|j|J|n|x]refpoint[+jjustify][+odx[/dy]] are common to all embellishments and determine the location of embellishments on maps.

The long option names are g|j|J|n|x for mapcoords,inside,outside,boxcoords,plotcoords, janchor for +j, and anchoroffset for +o.

This PR fixes the inconsistences in a few modules.

[joa-quim]

Yes, inconsistent we have it but I prefer to have all +j justify, and +o, offset than janchor & anchoroffset (which means almost nothing to me at first read. I found also the psbasemap case that has "...,janchor,offset".
And remember that changing these aliases normally make the respective test to fail too.

[seisman]

I've renamed anchoroffset to offset, but for +j, I think anchor makes more sense than justify, since it sets the justification anchor point.

[joa-quim]

OK, I'm not fully convinced about +j (after all the synopsis syntax says +jjustify and not +janchor) but won't insist on this.