Add "sukebei.nyaa.si" plugin + icon fix for "nyaa.si"

[Obegg]

Cloned the original "nyaasi.py", edited a few lines and now "sukebei.nyaa.si" is working.
Added an icon to "sukebei.nyaa.si".
And fixed the icon for the original "nyaasi".

You might wanna add "sukebei.nyaa.si.py" to the Unofficial search plugins (I leave it to you, the existing one there doesn't work)

Fixes #6

[MadeOfMagicAndWires]

Sorry about this; this PR somehow slipped by me; I've been rather distracted by health related issues.

I personally never really bothered with creating a sukebei plugin, as one was already available, but as I understand that plugin stopped working since, if you'd like me to merge this PR I still can.

[Obegg]

Never mind, I use Jackett now, it has everything I need.

[vt-idiot]

...I should have looked at the pull requests before reinventing the wheel.

Works great though! Thank you both. Looking closely at this PR, it seems that categories were not properly mapped to sukebei's. @MadeOfMagicAndWires if you want to use my implementation, feel free to. I'm a github newbie, not sure if I would have to open a PR from my fork or if you can do so.

[vt-idiot]

Actually, I went gungho with deletions and re-writing the license/readme. I can re-fork it and just upload the new script + icon if you do want me to make a PR.

[MadeOfMagicAndWires]

@vt-idiot a separate PR would be great thanks