Updated method names and argument orders of GerpFactory.
Changed the feature in GeneratorInfo from generators to generator.
Fixed compilation error in javac.

AbstractGerpExecutor.java:[117,21] incompatible types: cannot infer
type-variable(s) R,M,R (argument mismatch; bad return type in lambda
expression java.util.stream.Stream<capture#1 of ? extends
edu.cmu.lti.oaqa.gerp.uima.type.GerpBase> cannot be converted to
java.util.stream.Stream<? extends capture#1 of ? extends
edu.cmu.lti.oaqa.gerp.uima.type.GerpBase>)