Add error and exception handling

Currently there no real mechanic for handling errors and exceptions. Need to add errorState linked list struct and helper functions which should allow for added reliability and better error messages for users.

- [x] Define an ErrorState struct
- [x] implement helper functions
- [x] addError
- [x] retrieve head of error list
- [x] retrieve latest error
- [x] remove last error from list
- [ ] send error message to Slack
- [x] clear error list
- [ ] Update all functions to throw errors using new mechanic
- [ ] Define which function(s) catches errors.