Copy over the to-do list in mintpy to simplify the conda-forge recipe by @jhkennedy from #648:

• 1. test_smallbaselineApp.py and similar should look for configs relative to itself, not $MINTPY_HOME or mintpy.__file__

• 2. not printing on import:

  MintPy/mintpy/__init__.py

  Lines 18 to 22 in b307f96

  	try:
  	os.environ['MINTPY_HOME']
  	except KeyError:
  	print('Using default MintPy Path: %s' % (mintpy_path))
  	os.environ['MINTPY_HOME'] = mintpy_path

• 3. Drop any reliance on manipulating environment variables for installation (PATH, PYTHONPATH especially; MINTPY_HOME as well ideally) by leveraging console_scripts entry_points in setup.py

• 4. For pyaps3, read CDS key from $HOME directory, in addition to pyaps3/model.cfg file, so that users does not need to go to the interpreter directory for account setup.

• 5. arg-less main() and a work function. See the comment below for details.