Multisite

Hi!
I added multisite support to the plugin.
It adds an admin page in network admin. From the network admin, you are managing the network "site options" (wp_sitemeta table).
In multisite environments, bundle filenames are prefixed with "blog&lt;id&gt;-" or "network-" to avoid conflicts between blogs.
I also added a --network argument to wp-cli, for pushing/pulling network options (wp_sitemeta).