Improve compatibility code for global effects and particle emitters

Some values were being ignored, some were processed
incorrectly.
All legacy emitter levels I've tested now import correctly.
Closes #131
Fix typo in reading const_rot fields on emitters

Caused emitters with const_rot_z to be read and
displayed incorrectly.
Fix new particle emitter defaults

These are used when instantiating an
emitter from the editor menu, but were
using old field names, which caused the
editor to not emit anything.