Update to PyWB 2.7.x and resolve breaking changes

[anjackson]

There's a new PyWB on the way, with some significant changes: webrecorder/pywb#706

This includes e.g. moving the UI to Vue, which means it's likely that the ukwa-pywb theme modifications will break.

[tw4l]

The 2.7.0 release implements a new Vue banner and may (certainly open to opinions here!) drop the current default banner altogether.

If you'd like to move to the new banner, here's a sample of what styling it "out of the box" via config.yaml (specifying logos and colors per https://pywb.readthedocs.io/en/2.7.0-beta/manual/vue-ui.html) would look like:

There's also support for localization in the new banner, though it's not shown in the screenshot.

Making the change shouldn't be too difficult - we'll drop a few of the existing deprecated templates and static assets from ukwa-pywb, and modify the frame_insert.html template to use the Vue app without losing your GA keys and other customizations.

[tw4l]

here's a snippet of the ui settings from config.yaml to get the above result:

ui:
    logo: ukwa-2018-w-sml.png
    navbar_background_hex: 2e6dd9
    navbar_color_hex: fff
    navbar_light_buttons: true

[tw4l]

or with search bar centered (still working out the kinks of the new header layout):

[anjackson]

Woah thank you for that! Looks nice!