Allow user to reference land-use data for destination alternatives in destination choice models

[jfdman]

Currently there is no way to index into the land-use data file for each destination in the destination choice models. This makes it inconvenient to add district-district constants in destination choice. The only way to reference attributes of the destination (other than the size term and/or shadow price) is to develop a TAZ-TAZ skim where every row is exactly the same and every column is the destination zone attribute (state, district, jurisdiction, etc.) To add a district-district constant, the user can add the origin district to the choosers table in the preprocessor and compare to the skim value for the OD pair in the utility expressions.

We need to add functionality such that the user can directly reference attributes of land-use data at the destination end of the tour or stop location in tour destination choice and stop location choice models to improve functionality.