CLI output optionally target a folder

[Multihuntr]

Allows the user to provide a folder for 'target' using the CLI dat to json exporter, and it will create a separate file for each of the dat files in that folder.

That is, now you can run

pypoe_exporter dat json <folder>

And it will export all of the dat files as json to the specified folder.

I'm not sure what the error is exactly, but on:

AlternateSkillTargetingBehaviours.dat
AtlasExiles.dat
MapSeries.dat

I got the following error:

PyPoE.poe.file.specification.errors.SpecificationError: <ERRORS.RUNTIME_ROWSIZE_MISMATCH: 3002>: "AlternateSkillTargetingBehaviours.dat": Specification row size 16 vs real size 32

Since I didn't know what the problem was, I just excepted all errors. Let me know if this should change.

[OmegaK2]

It should raise any error but 3xxx specification errors. Those are specifically there to tell that the specification needs updating for the specific file, but skipping makes sense in this context, instead should just show the error.

http://omegak2.net/poe/PyPoE/_autosummary/PyPoE.poe.file.specification.errors.html#PyPoE.poe.file.specification.errors.SpecificationError