The previous heading was one size too small, and thus was easily
missed when visually skimming for the information.
Additionally, give it a more natural label.
Also link to it from the API documentation page,
other help pages, and the confirmation dialog for
muting a user.
With substantial edits by tabbott and alya.
We made this change because users often unnecessarily click "Home"
first in their use of Zulip, because it seems appealing. While "All
messages" isn't quite precise (it doesn't include muted streams), it
does describe relatively simply the interleaved view that this
represents.
This commit leaves everything as "home" in the code, and only changes
user-visible strings and docs. Changing the code will be a big project;
there are hundreds of relevant occurrences in variable names, etc.
Further, we'll probably want to convert those various variable names
in different ways.
Tweaked by tabbott to extend the commit message and update a few comments.