Adding an OOP analogue for StringUtils.splitPreserveAllTokens

[tjann7]

This pull request corresponds to issue #1722

Rationale of some decisions made:

1. Functional Interface allows use of custom String splitter function avoiding the static method calls
2. A new class created as modifying already existing Split class would not be shorter : if we add some checking for flags would create just as many constructors as with 2 distinct classes
3. Tests only compare lengths of obtained Collections