Add three features

Hi,

I added three features:

* `git_open_config_file` enables to open config file of the git repository.

* `git_open_config_url` enables to open url from git config file.

By default, it opens the url returns by the command:

	git config remote.origin.url


* `git_custom` improvement to execute several git commands in a row when they are separated by `;` and it enables to use it without `input_panel`. (I did not change the default behavior) 

For instance, you can define your name and email in one click:

    {
        "caption": "Git: User",
        "command": "git_custom", "args": {"command": "config user.name User;config user.email User@users.noreply.github.com"}
    }


Hope it helps.