Update teams management

Update styling to use Bootstrap 4. Make current user status clear.
Show member name as well as email address.
Make permissions impler to set on team admin form.

Update button styles

Replace Bootstrap 3 button default style with Bootstrap 4 equivalent.

Bootstrapification

Boot custom CSS, and put some base, standard css in its place.
Shame I did not start with fresh Bootstrap4, but oh well.

Some more templates could be made to make this less messy, which would
be good.