GROOVY-6379: Wrong example in the api of class Map(dropWhile)
GROOVY-6372: @Immutable fails to recognize non immutable classes (move the simple cases of matching on classname whitelist from runtime to compile time)
GROOVY-6384: add a direct method call logic for Class.forName(x)
GROOVY-6380: Improve Grapes resolution speed and stability by adding Bintray JCenter as first remote resolver in the chain

moved defaultGrapeConfig.xml for tests to correct test resource directory
Improve the grammar of a compiler error message
update copyright year
GROOVY-6357: Inner classes in Groovy should have the same access modifiers as in Java