Improve handling of geomean points with <5 samples

The map currently includes all geomean data points, even those calculated from fewer than five samples, in both the graphs (**confirmed**) and station status (**to confirm**). We should probably keep all geomean records in the dataset, but the map should either:

- Exclude geomean points based on fewer than five samples; or
- Display geomean points with five or more samples (either by default or as a toggled view), but provide users with an option to view all geomean points)

This recommendation is based on language in the statewide bacteria objectives, which states that a statistically sufficient number of samples is generally considered to be five or more ("Water Quality Standards Assessment").

Open to alternative approaches as well