Expose connected user data in wp.getOptions

To help the mobile apps help the user figure out which wp.com account
they're connected to, include user ID, username, and email in
wp.getOptions.

Also includes number of sites so the app can decide if it should suggest
Jetpack Manage.
Respect options parameter

wp.getOptions supports a parameter to specify the list of options to
return.

Respect that parameter by adding our options to blog_options instead of
filtering the result of wp_getOptions.
Merge pull request #1329 from Automattic/add/xmlrpc-expose-wpcom-user-data

Expose connected user data in wp.getOptions