first version of the us_inventory archetype in cyclus

[SamarAbdelkawy]

Summary of changes

Making the us_inventory module more capable of supplying spent nuclear fuel based on the user preferences based on discharge date, initial enrichment, and burn up.
I will keep editing the code as it still needs more functionality.
Also, I have added necessary build files based on the c++ tutorial on Cyclus website. I will probably need to tailor them more later.

Types of changes

• Bug fix (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 change)
• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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Associated Developers

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