fix: Remove JSON arguments in CLI

[nehanene15]

Removes JSON arguments in CLI. This fix is backwards compatible for JSON inputs if needed.
Includes README and docs/examples updates.

• Updated --tbls flag to accept tables in the form schema:table:target_table
• Updated aggregation flags to accept comma-separated lists
• Created --bq-result-handler which accepts project_id.dataset.table for result output
  • The original --rc flag is still supported. I created a separate flag for BigQuery so we can add new result handlers in the future with their own configuration parameters (in case they require more inputs than project_id and table_id).
• Updated --filters flag to accept string values

Closes #241

[dhercher]

I'm worried about this change, particularly to the tables. It removes the flexibility to select non-matching schemas on source and target. I personally use that feature quite often.

I'm worried about this being a breaking change, perhaps it doesn't need to be?

[nehanene15]

I'm worried about this change, particularly to the tables. It removes the flexibility to select non-matching schemas on source and target. I personally use that feature quite often.

I'm worried about this being a breaking change, perhaps it doesn't need to be?

Updated the PR to use the '=' operator mapping for tables. A table can be provided like so:
source_schema.source_table=target_schema.target_table

[dhercher]

lets leave this one as JSON formatting to test backwards compat?

[nehanene15]

Done 👍