Move trelis script automatically

[shimwell]

Proposed changes

Currently when running neutronics simulations users have to copy over the make_faceteted_gemetry.py script from the examples into the local folder. This PR performs this copy operation automatically. This reduces the burden on the user but unfortunately it introduces a script file that is difficult to test into the pacakge. It is difficult to test as we have no method of getting trelis into the dockerfile. The trelis script was previously in the examples folder but is now in the pacakge so the code coverage should drop a little bit. Is this acceptable?

Types of changes

What types of changes does your code introduce to the Paramak?
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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

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• Pep8 applied
• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)