Expose each OMPL planner as a separate OpenRAVE planner

I modified or_ompl to create a separate OpenRAVE planner for each wrapped OMPL planner. This replaces the ability to specify the planner name in the `PlannerParameters` struct. E.g. there is an `OMPL_RRTConnect` planner that calls RRT-Connect and an `OMPL_PRM` planner that calls PRM. Both of these planners show up in `openrave --listplugins`.

I also added a `GetParameters` command that returns the list of supported parameters.
It'd be nice to show an example of setting some extra PlannerParameters so that people don't have to hunt in the OpenRAVE documentation for figuring that out.