Returns a constant value notifying the system of
the general quality of the skill, whether it is
malicious, beneficial, indifferent, or qualifiably
beneficial (ok), as well as whether it is intended
to target the invoker (self) or others.
The achievement library forms the basis of the achievement system,
which accepts player events as input, as well as the file based achievement
definition files, and tracks player and account completion of achievements
A tracker object assigned to a particular player or account
for a particular achievement, allowing the achievement to
track progress if it needs to, or just providing a way
to quickly query completion otherwise.