Backport of specification from PhD thesis

- Add backport goal to Makefile to aid work
- copy the main chapter as "spec.tex"
- copy the rules appendix as "alethe_rules.tex"
- finish adaption of source code in spec.tex

spec/Makefile

+backport:
+	latexmk -pdf -pvc -interaction=nonstopmode -shell-escape -lualatex spec
+
 comments:
 	latexmk -pdf -shell-escape doc