Marker Annotations: Remove the old marker icon. Remove the left border colour (or make dark)

[villedigirati]

[cjcolvar]

@mcwhitaker This should be easy for the Avalon team to do. I think it would be nice to keep some way to differentiate the marker annotations from bubble annotations.

[joncameron]

This would be great. I'm in favor of removing the left border color altogether for Markers.