Add valid path check to new project wizard

[vkbo]

Summary:

This PR adds a simple check for valid path to the New Project Wizard. It isn't perfect, but it will eliminate most cases where the Wizard is completed but the new project not created due to issues with the path.

This PR also rewrites the tests for the wizard.

Related Issue(s):

Resolves #1058

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed