Macros guides stub

It is far from being ready for master.
Merge branch 'master' into macros
Don't link to a nearly duplicate Community page; the Design one is probably of little interest to beginners
Don't link to a nearly duplicate Community page; the Design one is probably of little interest to beginners
Unify title in both layouts
Move Security section down
Unify title in both layouts
Add an example for this section
Early version of the Macros guide
Merge branch 'macros'
Add Clojure Koans Walkthroughs playlist on YouTube
Cosmetics
Add Titanium and Hermes to the library directory
Cosmetics
Cosmetics
Cosmetics
Correct a heading
Updates to the Macros guide
This section is already [briefly] covered above
The Macros guide is complete enough now