Finalized Step 1 code, being changes to Step 2+3

Finalized Step 1 code to extract transect and square data for curlew and
avian predators (C.), as well as gamebird species (RL, PH, RG) and run
appropriate detectability models for the species of interest (CU and RG =
visit + vis, RL + PH visit  + habitat). Have begun to add environmental
data to dataset (Step 2) in preparation for running models (Step 3).