Hello! This PR resolves #44 that I opened about being able to rotate and split double panel images.

I try implementing it by myself, but, this is the first time that I wrote something in go.

All mangas that I downloaded with the news options worked just fine, but, the code itself can be a bit messy. Feel free to point to anything that you want me to modify in it.

What I added is:

Rotate and split double panel pages into two new pages.
It's possible to only rotate or rotate and split them.

Only rotating

--rotate or -H (H because Horizontally Rotate)

kojirou d86cf65b-5f6c-437d-a0af-19a31f94ec55 -l en --rotate

Rotating and splitting

--rotateAndSplit or -S (S because Split)

kojirou d86cf65b-5f6c-437d-a0af-19a31f94ec55 -l en --rotateAndSplit

If the line includes both of them, --rotateAndSplit will be the major one, --rotate still will run but it won't modify anything.

Anyway, before anything, thanks !
It really was a fun code to modify !