Change the remaining "Admin settings" with a button, namely
changing a stream's privacy, to instead be a "[Change]" link
opening a confirmation modal.
Fixes: #3493.
This removes the arrow from the subscriptions header at full
widths where the arrow is not required because the subscription
settings/stream creation prompt don't take up the full width of
the screen and require an arrow to go back to the streams list.
Fixes: #3762.
This makes the subscriptions page responsive by having the settings tab
slide over when a user taps on a stream, giving almost the whole screen
to view the settings.
Due to the fact that getComputedValue is called when using filter and
opacity attributes, it is much more efficient to use an SVG that has a
changing fill color rather than something that may be interpreted by
browsers as a layout change that requires layout recalculation.
This should result in noticeably smoother and more responsive :hover
events for the streams with greyed checkmarks.
This adds styling such that when you hover over a stream in the streams
list and you are not subscribed, you will see a faint grey checkmark
that serves as a target of where to click so you can subscribe to a
stream.
There is a case with browser zoom that the inline-block split view
breaks down and the two 50% tabs fall below each other. This prevents
that issue from happening.
This is a major change to the /#subscriptions page, converting it to
by a side-by-side list of streams and their settings in an overlay.
There are no new features added/removed, but it's a huge changeset,
because it replaces the old navigation logic and moves the stream
creation modal to appear in the right side of this overlay.