clean up removal of old files in _output when rerunning

[rjleveque]

In runclaw.runclaw, if paramters are set so that overwrite and (not restart)), it removes certain old files from _output, but only fort.* and gauge*.txt. See Line 163

These days there are numerous other files that may have been created in a previous run, such as gauge*.bin and fgout* files. In particular old fgout files cause a problem if the new run produces fewer files; some of the old ones will persist and might be included in a new animation that loops over all fgout files.

We should also revisit the related ancient issue #24.

[mandli]

Maybe we can come up with the list of commands we want and what we would like to have the capability to do from the Makefile system and map accordingly? Sounds like a good topic for discussion in an upcoming hack-a-thon.