turn time tracking on/off on per-project basis

We have only few projects that use time tracking feature; for others it's extra info they don't need to deal with – neither in viewing issue, search criterias, available actions on left-side action bar or even available reports.

We'd be happy to be able to turn off Time Tracking for most projects, leaving it available only when a team needs it.

Looks like the feature makes sense for a large organization where different teams have different usage disciplines on bugtracking.