- Avoid logging the same error over and over
- Make all the gray_errors actually warnings
- Replace `large_npl` error with `unstable_beam`, which is actually
the root cause of the former
- Use the gray_main error as exit code
- Replace the `get_free_unit` subroutine with the built-in
`newutin` option of the `open` statement.
- Replace `locatex` with just `locate` + an index offset.
- Replace `inside` with `contour%contains`.
- Merge `vmaxmin` and `vmaxmini` into a single subroutine
with optional arguments.
- Remove unused `range2rect`, `bubble`.
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.
