Improve error handling with snafu and eliminate panic calls

[ChristopherRabotin]

Effects

• [x] Switch from thiserror to snafu for better cascading of errors and in prep for #86
• [x] Remove all panic calls

Closes #190

If this is a new feature or a bug fix ...

• [x] Yes, the branch I'm proposing to merge is called issue-xyz where xyz is the number of the issue.

If this change adds or modifies a validation case

• [x] No.

[github-actions[bot]]

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[ChristopherRabotin]

Some panic calls still exist because they will be removed once ANISE is used (#86 ).