This PR adds preliminary parsing of parameters. Currently it only
supports 4 types: string, int, float32, and bool. Almost certainly we
will need to introduce more complicated parsing configuration (to handle
objects and arrays), but my initial attempts got quickly complicated, so
I simplified in the short term.
This also makes 2 breaking changes to config.yaml:
- changes "parameters" to be a list over object -- this is because
parameter ordering is important, and needs to be preserved
- removed the "required" field from parameter objects -- we need to
determine how to handle optional parameters in SQL queries
