Concept exercise progress

[colinleach]

I was getting confused about what needs doing to launch a learning track, and how to set priorities. The table below is one current view (taken from existing issues, the introcuction.md files, and an old flowchart from @SaschaMann).

There is no unique ordering for these, but I tried to ensure each exercise is listed below its prerequisites.

The concepts listed here cover most of the "Implemented" list in #566 but a few are missing: boolean-expressions, conditionals, integer-equality, using-macros. Some of these could probably be slotted in here, others need new exercises. None of the "Missing" list from #566 are covered.

Several exercises need stubs added #567, but I hope to submit a PR for that in the next couple of days.

slug	Introduces	Prereqs	Comments
lasagna	functions, integer-introduction, comments	hello-world	moved to production
documented-lasagna	docstrings	lasagna	largely complete?
annalyns-infiltration	booleans , boolean-logic	lasagna	largely complete
leap	arithmetic-operators	lasagna, annalyns-infiltration	replace?? #568
tech-palace	strings	documented-lasagna	largely complete?
vehicle-purchase	if-expressions, ternary-operator , short-circuit-evaluation	leap, tech-palace	#602
name-badge	nothingness	vehicle-purchase	largely complete?
elyses-enchantments	vectors, pairs	annalyns-infiltration	#580
elyses-analytic-enchantments	predicates	vehicle-purchase, vehicle-purchase, name-badge	#579
annalyns-infiltration2	randomness, methods, multiple-dispatch?	annalyns-infiltration	rename?? #571, needs into #572
exercism-matrix	matrices-introduction	elyses-enchantments	#586 #587
high-score	dictionaries	tech-palace, annalyns-infiltration2, elyses-enchantments	intro #599
dnd-char	kwdef	annalyns-infiltration2, others??	replace?? #576 #577
emoji-times	unicode-identifiers, emoji-symbols	??	#581 #582
encounters	multiple-dispatch	annalyns-infiltration2, others??	#583 #584
fibonacci-iterator	iterator-protocol	vehicle-purchase, name-badge, encounters high-score	#597 #598
stage-heralding	regex, string-literals-using	name-badge	#600 #601