Visibility - Add during placement only mode and max distance setting

[mharis001]

When merged this pull request will:

• Add "During Placement Only" mode to visibility indicator
• Add "Max Check Distance" setting - can range from 100 to 5000 m (same as hardcoded limit of lineIntersectsSurfaces command)
• Improve getPosFromScreen common function with parameter to control whether a flat position is return or just the first intersection
• Some minor cleanup of the visibility component
• Close #421