[replies] grey out replies box when the user is not logged in

[redshiftzero]

A user should not be able to send a reply when the journalist is not signed in. Instead the reply box should appear greyed out with a note indicating "please log in to reply to a source!" or something similar.

@ninavizz please drop any additional thoughts on this one!

As a not logged in journalist user, I want to see on screen how to reply to a source so that I know I need to log in.

Note: The PR that addresses this issue should revert the changes in f844108

[ninavizz]

So: the "top-bar" in the Client, should always show the text shown in these wireframes... but I dunno if the existing Client build, has such a bar. FYI.

To see Online/Offline, toggle on the top bar of this clickable(ish) wire: https://invis.io/X4QEP5Y9EAT#/345671069_0_New_-_DR_On-_OFFLINE

• Thinking that Delete Source functionality shd also go away in Offline Mode, but—ya—different PR/Issue, for a different day/PR/Issue. :)