Namespace package conflict with pftools

[vineetbansal]

It looks like there's a namespace conflict issue in the Subsetting code w.r.t pftools, since it uses the 'parflow' directory to install itself. This prevents its use along with pftools. A scenario in point:

- create a new conda environment and activate it.
- pip install pftools
- python -c "from parflow import Run" (works fine)
- pip install git+https://github.com/hydroframe/Subsetting.git
- python -c "from parflow import Run"

Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: cannot import name 'Run' from 'parflow' (/home/vineetb/.conda/envs/subset/lib/python3.8/site-packages/parflow/__init__.py)

If I only install Subsetter (which in turn installs pftools itself), using:

pip install git+https://github.com/hydroframe/Subsetting.git

Then there's the same issue again.