Optionally ignore certain values when inferring types

[yngve-sk]

The type inference got messed up by some "?" values in a dataset. Being able to (optionally) pass a regex to infer / inferAll and thus ignore certain values can solve problems like this.

Example

// Ignore any sequence of "?" entries
let typesIgnore = datalib.type.inferAll(data, data.columns, /^[ ?]*[?][ ?]*$/);
// Ignore nothing
let types = datalib.type.inferAll(data, data.columns);

Results:

[jheer]

Thanks! This is a useful feature to add.