This removes the old base button style which was a blue button and
kills the unnecessary .white class which was essentially just acting as
the new button base.
This then removes all references throughout the settings/subscriptions
pages to those button styles.
This also fixes the strange button styles that changed the :hover and
:active opacity to 0.05 which led to unpredictable results on various
backgrounds.
This changes the layout of "organization settings" for
non-administrators such that they can view "Default streams" ("Actions"
and the form to add new default stream is not visible).
This restructures the styling for the Zulip settings and
administration pages to minimize use of Bootstrap and use a consistent
styling library for similar elements.
While it is basically a wash in terms of the page's visuals, it will
make our life a lot easier for future work on improving the settings
pages section of the site.
Aditya Bansal
Brock Whittaker
digi0ps
Abhijeet Kaur
Vishnu Ks