Registered query: type verification of input parameters

[lukas-vlcek]

Type verification of input URL parameters will allow to perform needed checks before they are passed into search template. The main benefit is human friendly reporting of invalid input value (as opposed to ugly Exception trace from Elasticsearch).

This is also important from Mustache templating POW, because it can produce different result if a parameter is single valued or an array.

For example take template {{#param}}Hi man!{{/param}}. If the param is single value then it will produce:

Hi Man!

however, if it is an array with say 3 values then it will produce:

Hi Man!Hi Man!Hi Man!