Activates threading and hook features

Activates threading and hook features

Activation of threading was delayed until
CES demo.

Now that CES demo is on, threading can be
activated and tested in real.

This also enables new features:
 - Compiler fixes
 - Hooking of requests (for debugging)
 - Change in handling option --roothttp
 - Documentation improvements
 - Minor internal improvements and cleanup

Change-Id: I4c7052697a83c3d49a283970c502c62a5d3ddd64
Signed-off-by: José Bollo <jose.bollo@iot.bzh>
Signed-off-by: Stephane Desneux <stephane.desneux@iot.bzh>