cli/install.php - Add command-line interface to the installation system

Example usage:

```bash
git clone https://github.com/joomla/joomla-cms.git
cd joomla-cms
php cli/install.php \
   --db-user=myuser --db-name=mydb --db-pass=mysecret \
   --admin-user=admin --admin-pass=secret --admin-email='admin@example.com'
rm -rf installation
```

This is my first patch to Joomla, and the patch has a couple FIXME's which may require discussion. The main FIXMEs:
 * JApplicationCliInstaller::doExecute() sets "$options['db_created'] = 1" as a workaround. This shouldn't be necessary because InstallationModelDatabase tries to set that value by way of $session, but something's wonky with the handling of $session, and I don't know the ins-and-outs about JApplicationCli/JApplicationCms/JSession.
 * getLocaliseAdmin() has been brutishly copied-and-pasted from InstallationApplicationWeb to JApplicationCliInstaller. I don't particularly know what it's for, but it doesn't appear to depend on $this, so it could be safely moved to another class (where it's easier to share code).

exactly, the joomla installer application is also translated as the rest of the CMS. The Joomla installer provides already all the translations in it. See: https://github.com/joomla/joomla-cms/tree/staging/installation/language

But the language of the installation is not needed for the CLI script since the user will not see any installation app when using CLI