[Asterisk-doc] "The Extensions.conf Cookbook" chapter

[Olle E. Johansson]

To rip apart, if the subject is introduction to the dial plan (mainly extensions conf)
Haven't thought of it all, just shooting from the hip

BASIC
* Concepts: Channels, extensions, users, applications, contexts
* A general overview (how <channel>.conf  files and extensions.conf work together
* Handling calls
INTERMEDIATE
* Adding logic (macros)
* Using contexts
ADVANCED
* Special extensions (I,T,S)
* Building IVR
* AGI

Channel configuration is separate chapters
Zaptel configuration /dev kit lite/ must also be separate

Jared, I'm just thinking freely on how I would start. It's a very complicated thing
to describe, so it's important to start with the right approach. The old handbook
is not that bad in this part.

/O