Previously the typeahead container was being created at the bottom
of `body`, and its width (and `top` and `left`) were being set to
move it to the right position.
Now it sits in the search box container, which gives it the correct
position and width by default. This is better for DOM readability,
and is also better for the new 100% width (which is part of the
search bar redesign) because it can change width more smoothly
with the search bar when the page changes width.
This commit adds custom functionality to the bootstrap typeahead
to allow the typehead to be placed in the search box container
(whereas previously, it could only be appended to `body`).
Updates frontend user-facing strings with "private message" or "PM" to
use "direct message" or "DM" respectively instead.
Note that this updates translated strings as well as a few that
are not translated like search suggestions.
Updates `tools/lib/capitalization.py` for some specific strings
that are impacted by these changes, and removes "PM" and "PMs"
from checked strings.
This lets us simplify the long-ish ‘../../static/js’ paths, and will
remove the need for the ‘zrequire’ wrapper.
Signed-off-by: Anders Kaseorg <anders@zulip.com>