Add jquery-chosen library for pulldowns (MIT license)
Add start of Land Management model with land type and erosion

[#58011934]
LM: Add precipitation slider

[#58095824]
LM: Add zone labels

[#58159154]
LM: Add generic method for defining checkboxes as property controllers

[#58159154]
LM: Add show-erosion checkbox to show colors of zones

[#58159154]