fix docs for <subChainSelector>
(cherry picked from commit 496ef134b6e175509110254d0d265fcf3a2a1870)
rename ProblemIO to SolutionFileIO + split up input output file extension + force api/impl split in org.optaplanner.persistence
(cherry picked from commit 5c41bc494f1a342511f6764aa02ff32bdc33729b)