Extract play-functional module

This module is the first dependency which needs to be extracted to extract play-json.
Extract play-datavalidation

Second dependency which has to be extracted to be able to make play-json standalone
Extract play-json
refactored play-functional to make it clearer + moved Constraints back to play core project because I want to keep Forms as is for now
Extract play-functional module

This module is the first dependency which needs to be extracted to extract play-json.
Extract play-datavalidation

Second dependency which has to be extracted to be able to make play-json standalone
Extract play-json
refactored play-functional to make it clearer + moved Constraints back to play core project because I want to keep Forms as is for now
merged newest code coming from master
Merge pull request #754 from jeantil/extract-play-json

Modularize play-json / play-functional / play-datacommons