MultiDelimiterStringSearchInterpolator does not cache answers

[belingueres]

MultiDelimiterStringSearchInterpolator's cacheAnswers has no effect at all, since existingAnswers Map is never populated.

[slawekjaranowski]

similar to:

• RegexBasedInterpolator does not cache answers #20

[slawekjaranowski]

maybe we can drop at all cacheAnswers, as source are in many time a maps in memory why we need build another map