Allow custom filename format when creating ipfs directories

[roachcord3]

This might be similar to #426, but I think it's different because it's specifically about how directories are constructed, rather than individual file pins.

There should be an option to use a custom filename format string (just like when exporting files) for ipfs directory creation. Right now, all you get is {hash}.{filetype}. I would like to be able to do something like {filename} or {creator} - {title} - {page}.{filetype}.

I think this might be mutually exclusive with nocopy mode, but I'm not an ipfs expert, so I'm not sure. If it is mutually exclusive, then changing the filename format should disable nocopy mode, and enbaling nocopy mode should reset the filename format. This should be indicated to the user with a warning modal dialog or something like that, so that they don't get any unexpected surprises.