0.20.3

CHANGELOG

c94640c + improve js api
51892bb + full package
cffa538 + problog examples
ed7d867 + probablistic solver example
abc373f improve management of probabilistic operators
0183f5a make usage of Solver factories consistent with deprecations
acc711a add factories for prolog and problog solvers, and their tests
7153258 fix packages in solve-plp and solver-problog