Waves Markers: resolve performance issues when displaying markers

Fix an issue where multiple water patch markers are shown and not deleted properly except after a time out.

Details

Change the markerID's to be greater than zero, markers with markerID = 0 are not cleared correctly.
Resolve memory and performance issues when displaying markers.
Add functions to delete markers rather than rely on timeout.
Change colour of underwater surface to transparent green.

Figure: waterline and underwater surface markers now display correctly without multiple copies.

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Figure: water patch markers now display correctly without multiple copies.

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Figure: RM3 WEC device example.