Add option to schemes table to use cache for maindisplay results

[kjolley]

Scheme field results for large schemes like cgMLST can take a few 100ms per isolate to calculate, which is fine for display of a single isolate record, but can lead to a noticable delay in populating a results table of 25 or so records.

We could add an option to a scheme to use the scheme cache for this - currently it is only used for queries and exports.