add command generation options

This permits to avoid looong commands in your shell history.
Just explode a long suite of command by replacing ` && ` with `\n`.
Also permits to not export `TEAMOCIL=1` env variable.

Just configure your window like that:

``` yaml

session:
    name: <%= File.basename(Dir.getwd) %>
    windows:
        - 
            cmd_separator: "\n"
            with_env_var: false
            name: editor
            splits:
                - { cmd: vim }


```