1. Use the `contour` type for limiter and plasma boundary
(rlim, zlim, rbnd, zbnd)
2. Replace `inside` with `contour%contains`
3. Replace `range2rect` with a `contour` interface
4. Remove the limiter module which just re-exports the limiter
as a global; instead just pass the contour object around
This change replaces the output files (Fortran units) with a derived
type called table, that hold the data in memory until further
processing. The data stored in a table can be dumped to a file, as
before, or processed in other ways, for example converted to other
derived type.
