Untested functions in Doltpy

There are a number of untested functions in `doltpy.core` that were introduced to in 1.0.0 to match the CLI. A list of them is:
- `reset`: no testing, `hard` and `soft` modes need to be tested
- `diff`: no explicit testing, not used in testing, currently just prints output, we may want to rethink this to use some kind of objects or bind it to queryable diffs and populate the diff in a DataFrame type structure
- `blame`: no explicit testing, not used in testing, currently just prints output, like `diff` might benefit from being stored in a programmatically accessible data structure
- `push`: not tested, and actually missing a host of more escoteric options that exist in the CLI
- `pull`: same as `push`
- `fetch`: same as `push` and `pull`
- `clone`: again, untested
- `creds_*`: untested
- `config`: untested
- `schema_*`: no testing, and not clear what the interface should be given that it can do a number of things
- `table_*`: no testing, and not clear what the interface should be given it can a number of things

Incomplete testing:
- `commit`: used in testing but `date` and `allow_empty` not tested
- `sql`: basic query execution is tested but non the others modes (`result_format`, etc.)
- `sql_server`: most basic execution of query tested but not other modes
- `branch`: basic branch creation is tested, but `force`, `start_point` etc., are not.
- `checkout`: used in basic testing of `branch`, but `start_point` not tested
- `ls`: no testing of `system` and `all` switches

Others that are used in tests but not explicitly tested:
- `init`: no explicit tests but relied on by other tests
- `add`: no explicit testing, but used everywhere in tests

I think we can just reference use this ticket to hash out a plan for testing (what needs to be tested and the priorities) and interface design, as there are few functions that would benefit from a programmatic interface, not just printing a string.