Makefile fixmes

[cdlm]

Style :

• cp -r should be cp -R
• phony targets should be declared
• copySupport.mk being a separate file makes little sense

User-friendlyness :

• a sensible default target should be defined
• presence of dependencies fetched by subdownload.sh should be checked by the makefile
• should run ./gitinfo2.sh >> book-result/gitHeadLocal.gin before building the book

[cdlm]

Superseded by pillar-markup/Pillar-Archetype#2; will require backporting the fixes here