[lang][text] New case conversion util

[Gary Gregory]

Too weird for lang or text:

public enum LetterCase {
    LOWER {
        @Override
        public String toCaseString(final String source, final Locale
locale) {
            return source.toLowerCase(locale);
        }

    },
    UPPER {
        @Override
        public String toCaseString(final String source, final Locale
locale) {
            return source.toUpperCase(locale);
        }
    };

    public abstract String toCaseString(String source, Locale locale);
}

?

Gary