Move destructive mvol options into a new command.

[johnjung]

Several options on the mvol command are destructive- they make changes to the files in OwnCloud:

• mvol put_dc_xml
• mvol regularize_mets
• mvol regularize_pdf
• mvol regularize_struct
• mvol regularize_txt
• mvol rename_altos
• mvol rename_jpegs
• mvol rename_tiffs

In order to make it clear to the user that these options change files on disk, move them into a new command called "mvol_fix".

This command should use docopt for argument parsing, just like mvol, and it should include the destructive options listed above. Those options should be removed from the mvol command.