The server section was only in the directory menu, which a conversation's
header replaces with its title menu, so servers could only be switched from a
new conversation. It is now a shared ServerMenu at the end of both menus
(switching starts over on the other server, since conversations belong to it).
Server rows used the default one-line item height for two lines of text; they
now use the directory rows' 44px two-line layout. The lists above shrink to
leave room for it; the History icon's menu, without a server section, keeps
its height.
Verified: typecheck, lint, build; the extension reloaded into the new build
in the user's Helium (relay reports the new build id).
Ryan Vogel
fd06f8f785