Divide Basic Acronym and Advanced Acronym

1) We are short on really easy exercises
2) The easy exercises we do have, tend to get more complex over time because of added tests for edge cases
3) There are several proposals (open and closed, implemented and not) to add cases to the current Acronym
4) Adding one or two more tests will not provide a powerful Acronymizer; that needs a more thorough analysis (especially of establishing a limit of how powerful we'd like such an advanced Acronymizer to be.)
5) Exercism is not meant primarily for practising with regex

=> Proposal:
1) Keeping the current Acronym as simple as possible, such that 'splitting on spaces' will not do, but not pretending that we're offering a real solution for creating Acronyms.
2) Create a new, advanced Acronym, that catches a much broader range of edge cases.

It would be another series of exercises, like the [recently introduced Resistor series](https://github.com/exercism/problem-specifications/issues/1458), with advancing complexity.