Improve Javadoc for AreIn, IsIn and CollectionContains

[GCHQDeveloper314]

Currently the JavaDoc is quite basic for these classes in Koryphe. In particular the handling of null and empty values for functions and predicates is not explained sufficiently well.
For CollectionContains the Javadoc states that it "checks if a collection contains a provided value" and it is able to check for if a collection contains null values. The name CollectionContains explains this functionality to some extent. The situation is not so good for IsIn and AreIn. The language should be clearer with less of a fix of words with similar meanings.