Prioritize settlement lands, trapping concessions, and placer/quartz claims in cell selection

[prvernier]

I've created a preliminary function to force cells with settlement lands into random samples. Next steps:

• Need more flexibility: currently hard coded for >50% of cell in settlement lands to be included
• Test to make sure it works as expected
• Seems some layers no longer visible after generating sample. Should this be a separate issue?
• Add similar functionality for trapping concessions and placer/quartz claims.