- Store user theme in session
- Logged out users will keep their theme
- Add theme background color to web manifest and meta tag

- Increase truncate length to 35 chars for feed titles
- Add bottom margin for main menu in mobile view
- Add tooltip to feed domain in feeds list

Adds IMAGE_PROXY configuration setting to change image proxy filter behaviour:

- none = No proxy
- http-only = Proxy only non-HTTPS images (default)
- all = Proxy everything

Avoid this warning in Chrome console: https://www.chromestatus.com/feature/5745543795965952

Searches tags for various `data-*` attributes and sets `img` tag `src` attribute appropriately. Falls back to searching `noscript` for `img` tags.

Includes unit tests.

- Using autocomplete="off" or autocomplete="new-password" doesn't change anything
- Changing the input ID doesn't change anything
- Using a different input name doesn't change anything
- Only Chrome supports autocomplete="new-password"

Addresses #163.

Updated iframe unit tests.

Refactored sanitizer.getExtraAttributes() to use `switch` instead of multiple `if` statements.

using vendor-specific CSS `*-text-size-adjust`.

Browsers always autocomplete saved passwords even with autocomplete="off".

https://developer.mozilla.org/en-US/docs/Web/Security/Securing_your_site/Turning_off_form_autocompletion