User Services/Sync/v2

User stories moved from MVP

• NEW As a user, I want optionally to specify which types of data will be synced between my devices. During this process, I want to be able to get more information about what each type of data is, what that data means in terms of my browser functionality, and what happens to that data when I have logged out of my browser.
• NEW As a user, I want to be able to modify my Sync data settings in my browser at any time after I have set up Sync and am logged into my Firefox Account.
• NEW As a user, I expect that my Sync settings will be applied universally across all of my devices, so if I change which data types I'm syncing while on my phone, those changes will apply to all of my data types. (Note: we may want to change this to being device-specific settings in the future, so please ensure we can change this later if needed.)