Throttle Quadrant Quick Release Lever Handles

Added a quick-change connector to the levers of brettkp's Throttle Quadrant. Goal is to make it easy to switch the quadrant to match controls of different types of planes, e.g. a modern single engine turboprop (example provided) to a twin engine, to a tubeliner (exercise for the reader) or anything else. This replaces the original levers, but no other parts; fit should be identical.

The levers are modified to have a male side-release connector (common buckle in outdoor gear), but are otherwise identical (gearing and mounting point) to the original lever; they should be drop-in replacements. The "buckle" parts are included to help further remixing, and an example set of levers, based loosely on a modern turboprop (Quest Kodiak), are provided. Of course, a set of 4 or more straight levers could be used to model a twin, or a jet, etc.

[EDIT -- this does not work well, don't use as provided]: Minor additional modification is a simple tension-release mechanism to enable typical ai