Please add conditional options to content/layout blocks.

The conditions should allow us to check if a given subscriber is in a segment or has a given tag, in order to show/hide the content.

This could for example be used to show VIP content only to VIP members (e.g. 1 VIP-only block with a coupon code, but the rest of the newsletter is identical), or show different content for different languages, without having to build various different newsletters each time.