Improve WordPress Multi-site Support

Bug Report

Tell us about your setup
WordPress Multi-site from Pantheon

What is your lando version and operating system?
lando-v3.0.0-alpha.13 on Running Mac OS Sierra 10.12.5

Have you previously installed lando? If so, what version?
No

Tell us about your bug
I don't think Lando plays well with WordPress Multi-site.

Please detail the steps we can take to replicate this bug. Be as detailed as possible.

1. Ran `lando init pantheon
2. Filled in crendentials
3. lando start
4. Error:

warn: wordpress_network is not a supported recipe.
error:  TypeError: Cannot read property 'filemount' of undefined

5. If I change my framework to just "wordpress" instead of "wordpress_network" which was set by default, I can proceed forward.
6. lando start
7. No longer a frameworks bug, but I get a:

PHP Fatal error:  Uncaught Pantheon\Terminus\Exceptions\TerminusException: Could not save data to a file because the path /var/www/.terminus/cache/commands cannot be written to. in /var/www/.composer/vendor/pantheon-systems/terminus/src/DataStore/FileStore.php:155

8. lando restart
9. Things appear to be normal...
10. Setup finishes. 2 of the URL's are in red. 4 on in green.
11. Let's try one of the links: http://localhost:32787 - "Site cannot be reached"
12. I can remove these two lines in my WordPress wp-config.php file:

define( 'WP_ALLOW_MULTISITE', false );
define('MULTISITE', false);

13. Head back to: http://localhost:32787 - WordPress wants to start installation.
14. Successfully imported the database using the Lando documentation
15. In order to check my multi-sites, I need to turn true the items in Step 12. However when I do so, I get:

Error establishing a database connection

If I can just get this last part working I'll be golden, everything else is working great! @pirog

Feature/Enhancement Request

Would love to see WordPress multi-site support!

Start by reproducing the wordpress_network failure with lando init and lando start using the Pantheon setup described. Inspect the WordPress multisite settings in wp-config.php and verify that setup completes, multisite URLs are reachable, and the imported database connects without errors.