Advanced user installation instructions use deprecated pip feature

[dallan-keylogic]

The instructions in the advanced user installation tell the user to pip install -U . as part of updating IDAES. That results in a deprecation message:

(idaes-new) C:\Users\[REDACTED]\idaes-pse>pip install -U .
Processing c:\users\[REDACTED]\idaes-pse
  DEPRECATION: A future pip version will change local packages to be built in-place without first copying to a temporary directory. We recommend you use --use-feature=in-tree-build to test your packages with this new behavior before it becomes the default.
   pip 21.3 will remove support for this functionality. You can find discussion regarding this at https://github.com/pypa/pip/issues/7555.

Edit: And this issue came back to haunt me. Without the -e or --use-feature=in-tree-build flags, pip install -U . installs the IDAES repo in its current state to a temporary directory somewhere else. When the -e flag is included the directory containing the IDAES repo is added to the PYTHONPATH (which is what I wanted). This Stack Overflow answer says:

This is the "same" as using the --editable flag: the source of the package is used as the source of the installation without any copies being made.

The scare quotes around "same" make me think there must be at least some difference, but I wasn't able to discover it during a short search.

[lbianchi-lbl]

The current Update IDAES paragraph is inaccurate (or at least inconsistent with the rest of the document) since it results in a non-editable installation. We should update that part of the docs so that it reads e.g.

pip uninstall .
pip install -r requirements-dev.txt

[mli93]

pip uninstall . was not recognized by pip. pip uninstall -r requirements-dev.txt worked.