Improved support for path templates (#110)

* initial path template support updates

Author: rsgalloway

examples/default/test.env

@@ -3,6 +3,7 @@ include: [default]
 all: &all
   PYVERSION: $(python -c "import sys; print(f'{sys.version_info[0]}.{sys.version_info[1]}')")
   PYTHONPATH: ${DEPLOY_ROOT}/lib/python${PYVERSION}
+  NUKESCRIPT: ${ROOT}/projects/{seq}/{shot}/comp/{show}_{seq}_{shot}.{version}.nk
 darwin:
   <<: *all
 linux: