Provide an extension for the max file upload size

By default, this will up to 100MB for sites that have been given
extended permissions
Display option to apply extended permissions to a site on the network
Save a request to apply or deny extended permissions to a site
Allow csv, keynote, numbers, and pages uploads at the basic level
Super admins (global admins) have the ability to upload exe

I'm still not entirely sure how I feel about this, but we can start
by restricting exe uploads to those with super admin access, which
is really a small handful.

Once we figure out what automated virus scanning could look like, this
could be implemented at a wider level