Proposal: nf-core-utils

This will swap all of the functions and subworkflows into a [plugin](https://github.com/nf-core/nf-utils). It should be much cleaner for updates from users. ## Outstanding things to test(I'm just not a regular user of these features): - [ ] imNotification - [ ] email notification ## Things that still need fixing/re-working on nf-utils: - [ ] Citation management - [ ] Colors on `ERROR ~ The `-profile` option cannot end with a trailing comma...` - [ ] Refactor `workflow.onComplete` and `workflow.onError` into a traceObserver