Dryrun

I changed the --dry-run option so that when using it outside of running tests it does not create the project directory or copy the blueprint template when it is used running:

```bash
$ ember new foo --dry-run
```
```bash
$ ember init --dry-run
```
The current implementation when running `ember new foo --dry-run` would create the foo directory and populate it with the blueprint template. When running `ember init --dry-run` the current implementation would populate the directory with the blueprint template. This behavior to me seems unexpected as I would expect running --dry-run would not actually create anything but just print out what it would have done without the --dry-run option.

I added an --init option that would provide the behavior that --dry-run currently does:

```bash
$ ember new foo --init
```

This will create the foo folder and copy the blueprint template but does not install the npm and bower modules.

```bash
$ mkdir foo && cd $_
$ ember init --init
```

This again will copy the blueprint template but does not install the npm and bower modules.