Lint Suggestions

[chappertron]

Lints are sanity checks on the input scripts. Some can be severe and some can just be warnings.

The only currently implemented lint is a work in progress, one that checks if a fix is redefined multiple times before a run command occurs.

Some ideas for future lints:

• [ ] Warn about modulus argument for fix berendsen being missing.
• [ ] Error if multiple integration fixes are defined.