Choko command

### How it works:
```
choko start
```
- If the file "./applications/applications.json" exist, will just start the application.
- If not, will create the default directory for applications (in case it not exist already), run the install process, and then start the server in order to continue the install process in the browser.

```
choko start sandbox
```
- If the file "./sandbox/applications.json" exist, will just start the application.
- If not, will create the specified directory for applications (in case it not exist already), run the install process, and then start the server in order to continue the install process in the browser.

So you could start a new application just doing:
```
$ mkdir my-project
$ cd my-project
$ choko start
$ tree
└── applications
    ├── applications.json
    └── localhost
        └── settings.json
```
I did it in that way, because isInstalled() is used by the start() and could be used in others. So I thought it would be interesting to maintain all the "helpers" in the top of the file, seems more predictable, what do you think?

Comments are not always good, but in this case I agree strongly with you! I'll comment that out :)