Add global settings

[LasmGratel]

1. Add a panel to select the default settings(like I always use Independent Run Directory)
2. Add JSON Editor.

[huanghongxun]

Advice 1: might be redundancy, two panels which look like the same? Not a good idea.
Advice 2: If you want to modify JSONs, you are sure to know the syntax. So what does a JSON editor stand for? A person who does not know what JSON is? It wont want to modify JSONs because it has no requirement here.

[nickzyc12]

I agree with the author's opinion.
I just know nothing about JSON (before I google it...) and I believe that the most of the users of this luncher are similar to me. Therefore, I don't think a programming language editor is necessary.

[LasmGratel]

@huanghongxun Not a public JSON editor, I just want to edit .json and Forge Mod's configuration.

[huanghongxun]

Accepted by commit a11ca8b