Adds --noDownload option to InstallCommand

`--noDownload` option is useful when Magento is already stored in the `--installationFolder` and should be only installed on the given database.

So the `--noDownload` option skips the download of Magento and uses the one already stored in the `--installationFolder`.

This option could be useful when a developer needs to install Magento that has been already cloned from a private repository, for example a respository with a customized Magento installation.