Support -checkdate, -skip, and -continue options from original munge apps

From the `MUNGEAPP` help text:
```
-CHECKDATE (only munge if output is out of date)
-SKIP (do nothing - useful in option files)
-CONTINUE (continue after error)
```

Start at the MUNGEAPP command-line entry point and its option handling. Use the help text as the behavior reference: CHECKDATE should skip up-to-date output, SKIP should do nothing, and CONTINUE should proceed after an error. Confirm each option is accepted and behaves accordingly.

Written by the indexing model from the issue text.