Restructure Table of Content.

Signed-off-by: crynobone <crynobone@gmail.com>
Merge branch '2.0' into 2.1

Signed-off-by: crynobone <crynobone@gmail.com>

Conflicts:
	src/contents.md
Small tweak.

Signed-off-by: crynobone <crynobone@gmail.com>