Add is_ghe_start_loop to the URBANopt UI

[tanushree04]

is_ghe_start_loop is a required property in the GeoJSON file for Ground Source Heat Pump Sizing.

This is the schema for the property:
https://github.com/urbanopt/urbanopt-geojson-gem/blob/develop/lib/urbanopt/geojson/schema/thermal_junction_properties.json#L50

This can be added to the UI, so that the junction connected to the GHP is assigned this property on creating a Feature File.