JavaIntegration: Java-only String methods

[kindlich]

In ZenCodeLang/StdLibs#3 we defined methods for Strings that should be part of of StdLib.

Here we define methods that should be added only for the Java-Part.
Whether they be have to be added manually by whoever consumes ZenCode or will be added for any JavaProject will be decided while implementing this issue.

Methods in question:

• codePointAt, codePointBefore, codePointCount, codePoints
• contentEquals
• format
• intern (other languages may still have it though.. but no guarantee)
• lines
• matches (no regexes in stdlib yet)
• offsetByCodePoints
• regionMatches
• replaceAll (no regexes in stdlib yet)