Migrate old, useful content from old docs site

[oubiwann]

I keep using the old docs site for some things (such as the list comprehension examples). Lets get that content moved into the manual, and then just link to it from the other pages.

Content to move:

• Integrate useful intro material - Old docs site: Integrate useful "intro" material #21
• We can rescue the diving in parts - Old docs site: Integrate useful "diving in" material #23
• Lists and simple data sections - Old docs site: Integrate "Lists & Simple Data" chapter #25
• Much of the recursion can be rescued: http://docs.lfe.io/current/user-guide/recursion/1.html
• Mnesia tutorial: http://docs.lfe.io/current/tutorials/mnesia/1.html
• Some of the project setup stuff: http://docs.lfe.io/current/user-guide/devops/1.html
• For all content that is moved, add a redirect to the new location

Everything else can be scrapped.