qcABC, enqueue_notice, enqueue_error

Referencing: https://github.com/WebSharks/Quick-Cache/issues/172

- I tweaked `qcABC` just a bit so it will support any boolean-ish value.
- I added two methods; `enqueue_notice()` and `enqueue_error()`; and implemented these throughout the entire codebase for both QC lite and QC pro. This should help us keep Quick Cache [DRY](http://en.wikipedia.org/wiki/Don't_repeat_yourself); i.e. to reduce the number of times we need to repeat the process of pulling the array of notices, errors, and modifying the array in various places.