Illustrator compatibility

[mdtusz]

These changes are small, but they will allow Illustrator to open most plots now - some will still cause Illustrator to crash and will render incorrectly, but debugging is slow and done nearly blind.

In brief:

• remove the invisible draglayer svg elements
• ensure that geo background fills use fill and fill-opacity as opposed to rgba colors.

Long term, we need to ensure that all colors are applied as rgb and if there is an alpha, use the Color.fill or Color.stroke methods where possible.

[etpinard]

nicely done. 💃