Add comments on db unique indices
Add comments on db unique indices

These comments are later going to be used to expose a sensible error message to the user on duplicate conditions.
Also:
 * moved unique on ip_net_pool from name to schema/name.
 * add a bunch of NOT NULL constraints on various columns.

bbaja42/NIPAP,SpriteLink/NIPAP,plajjan/NIPAP,SoundGoof/NIPAP,ettrig/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,bbaja42/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,SoundGoof/NIPAP,bbaja42/NIPAP,fredsod/NIPAP,fredsod/NIPAP,ettrig/NIPAP,bbaja42/NIPAP,bbaja42/NIPAP,fredsod/NIPAP,fredsod/NIPAP,ettrig/NIPAP,SoundGoof/NIPAP,garberg/NIPAP,SpriteLink/NIPAP,plajjan/NIPAP,garberg/NIPAP,garberg/NIPAP,garberg/NIPAP,plajjan/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,fredsod/NIPAP,SoundGoof/NIPAP,plajjan/NIPAP,garberg/NIPAP,ettrig/NIPAP,plajjan/NIPAP,ettrig/NIPAP,ettrig/NIPAP,garberg/NIPAP,plajjan/NIPAP,SoundGoof/NIPAP,fredsod/NIPAP