Splitting and grouping side quest (#595)

* First draft of splitting and grouping side quest

First draft of a splitting and grouping side quest.
This includes separating samples using filter, then grouping and spreading by intervals.

Early version but introduces key operator concepts to participants.

* Spread over intervals prior to grouping

This commit reverses the order to spread over intervals prior to grouping. This achieves two things:

1. It explains everything once and only once to make the tutorial simpler
2. It provides a real world reason for using groupTuple

This makes the flow of the tutorial easier to understand, at the cost of very verbose outputs.

* add splitting and grouping to nav bar

* Add before/after to first code change

* Add ch_* prefix to all channels for clarity over objects

* Remove "pipeline" from opening statement to focus on channels

* Add "you will" statement to the beginning of the tutorial

* Fix typo and phrasing about combining

* Refine explanation of intervals and the combining method

* add another before/after snippet

* Use single BAM as input file

* Remove dump from tutorial to simplify and focus splitting-grouping and not debugging

* Update samplesheet

* fixup: Remove TODO

* Finish with a section on flattening the data to close out grouping

* revert main.nf

* Sort out notes

* Re-order side quests slightly for more logical order, from least to most complex

* remove intervals file

* Add earlier map to simplify data as core concept instead of challenge

* Tidy code up a bit

* Fix side quest order

* Reduce examples and left shift for clarity

* Fix typo in path to splitting-and-grouping

* Fix samplesheet items to be more consistent

* More consistent phrasing of first steps

* Apply suggestions from code review

Co-authored-by: Friederike Hanssen <[email protected]>

* Add reference to join documentation

* Fix headers and indentation

* Rename splitting and grouping file to be consistent with other filenames

* Refine summary messages

* Use bullet points instead of numbers for key concepts of splitting-and-grouping

* splitting and grouping use before/after correctly

* Splitting and grouping highlight lines

* fixup

* Fix formatting issue

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Co-authored-by: Friederike Hanssen <[email protected]>

Author: adamrtalbot