Import CSV data

[rolyp]

We need to support ~20k records for larger examples, perhaps loaded into a 1-dimensional array type, rather than a record, to avoid having to track dependencies on list nodes.

• [ ] openDatasetAs' which loads CSV rather than Fluid module
• [ ] Migrate existing openDatasetAs to new method

Done/dropped:

• Primitive to open file and return contents as list of records – defer for now as will require interpreter to support I/O
• Use CVS validator to generate a schema, and then use schema to generate a record type?

[rolyp]

Might need this if we switch the renewables example to take a dataframe as input.

[rolyp]

Bumped this to Pending as we need this sooner rather than later. Pared back to just replacing the current behaviour of openDatasetAs, which should be less intrusive than trying to support file loading in Fluid itself.