#2 YAML reading should skip header/footer lines

[Anna Wojtowicz]

The MOOSEFileHandler is currently "smart" enough to skip over extraneous header/footer lines for reading the action syntax file, but not the YAML file. This forces the user to manually remove these extra lines themselves. The YAML reader should be "smart" as well to just skip this stuff.

[Anna Wojtowicz]

I added a MOOSEFileHandler.createCleanMOOSEFile(...) method which will take in either a YAML or action syntax file, check if it has a header/footer, remove them if necessary, and overwrite the original file. It won't bother messing with the files on the filesystem if no header/footer is found.