Support override parsers in AutoDetectParser

In some situations, being able to specify an alternative parser is useful even when the general parser framework/full set of parsers is desired.

For example, when processing HTML documents the current HtmlParser doesn't pass through all of the tags that a vertical crawler might want.

I'm proposing an alternative constructor, something like:

public AutoDetectParser(Map<class, Parser>)

where class would be the class of the standard Tika parser, and Parser is the override.