GARNET as a python package

[searscr]

Short description of the changes:

This PR creates the foundation for installing GARNET as an editable python package.

Long description of the changes:

package has been setup so that

Using:

python -m pip install -e .

GARNET will be installed in your working environment and can be called as

python -m garnet

Or simply,

garnet

to start the application.

Check list for the pull request

• I have read the [CONTRIBUTING]
• I have read the [CODE_OF_CONDUCT]
• I have added tests for my changes
• I have updated the documentation accordingly

Check list for the reviewer

• I have read the [CONTRIBUTING]
• I have verified the proposed changes
• best software practices
  • all internal functions have an underbar, as is python standard
  • clearly named variables (better to be verbose in variable names)
  • code comments explaining the intent of code blocks
• All the tests are passing
• The documentation is up to date
• code comments added when explaining intent

Manual test for the reviewer

References

[mpatrou]

garnet is installed with pip locally.