BlendedInfixSuggester to support exponential reciprocal BlenderType

The orignal BlendedInfixSuggester introduced in LUCENE-5354 has support for:

• BlenderType.POSITION_LINEAR and
• BlenderType.POSITION_RECIPROCAL .

These are used to score documents based on the position of the matched token i.e the closer is the matched term to the beginning, the higher score you get.

In some use cases, we need a more aggressive scoring based on the position.
That's where the exponential reciprocal comes into play
i.e
coef = 1/Math.pow(position+1, exponent)
where the exponent is a configurable variable.