Fix auto-calc of prefix type on from-prefix add
Fix auto-calc of prefix type on from-prefix add

Changes the logic behind auto-calculating the type of a new prefix when
using from-prefix. We previously used a 'contains' operator, but that
only works for manually specified prefixes. 'equals' is used for the
from-prefix case.

Fixes #462.

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