Allow specifying type of field for parameters

[petrsvihlik]

Motivation

new OrderParameter($"elements.{Article.PublishDateCodename}", SortOrder.Descending)) is not very nice.

It would be great if OrderParameter (and perhaps some others) allowed specifying the type of the codename parameter.

Proposed solution

new OrderParameter(FieldType.Element, "Article.PublishDateCodename", SortOrder.Descending))

The enum could be defined such as:

enum FieldTypeEnum
{
 Element,
 System,
....
}

Originally reported in #241 (comment)