tree should set up proper module file environment variables

[havok2063]

This tree product currently does not set up the proper expanded module file with all the envvars set. It cannot currently be used strictly in modules environment.

[havok2063]

This has now been fixed in master. I've refactored the bin directory to include a setup_tree.py script. This code will set up the SAS_BASE_DIR, create the module, bash, and tsch environment files in etc, and copy them into a user's defined modules directory for the tree. If the SAS_BASE_DIR and the modules directory are not defined, it prompts the user to define them. I think it captures all of the behavior of the original bin directory but someone should check that. I've added an entry into the invoke task.py to run this. To set up the tree from scratch, a user checks out the tree repo, cds into the main directory and runs invoke setup-tree [OPTIONS]