"Add to bookmarks/read-later" RS option for links posted to a channel

[raucao]

The awesome power of RS really comes into play when wiring up access to the same data from different apps. In this case, we can e.g. store bookmarks from Hyperchannel and then access them in Webmarks.

(Another case would be sharing files via the shares module, then accessing/searching history in both Sharesome and Hyperchannel itself.)