Tentative android support. Tentative as in, it won't break desktop. The usual debugging toolchain doesn't work right now, so I need to publish to test. More details at: https://blog.mozilla.org/addons/2020/09/29/expanded-extension-support-in-firefox-for-android-nightly/ .

fix a bug introduced in FF61 when using private browsing mode
misc style fixes

- styled the options page for ui consistency
- work around a bug where an empty url input passes validation
- guard against restored windows potentially having their initial tabs redirected
- update icon color for consistency

- fixed a bug that caused the first tab of a new window to be redirected
- use loadReplace when updating a tab
- don't redirect tabs with TAB_ID_NONE