Add `baseField`, `baseOperator`, `baseCombinator` object props

[jakeboone02]

Description of the feature

Add baseField, baseOperator, baseCombinator object props that each respective object would be spread on to.

Use case

Allow users to define properties common to all similar objects, overridable by the standard, existing configurations.

Usage:

<QueryBuilder
  baseField={{ datatype: 'string' }}
  fields={[
    { name: 'f1', label: 'F1' },
    { name: 'f2', label: 'F2', datatype: 'number' },
  ]}
/>

Internally, the fields array would be augmented something like this:

const fields = props.fields.map(f => ({ ...props.baseField, ...f }));

So the fields prop would effectively be:

[
  { name: 'f1', label: 'F1', datatype: 'string' },
  { name: 'f2', label: 'F2', datatype: 'number' },
]

Other prop name style possibilities: templateField, fieldTemplate.

Type will probably be Record<string, undefined>.