Incorporate WK Mobile's internal browser and userscripts support

This commit brings support for userscripts and fixed issues with the review system caused by the built-in webview.

Userscripts available as of this commit:
- Ignore Button (WaniKani Override)
- Single Button
- WaniKani Improve
- Review Order
- Lesson Order
- Auto Popup
- Mistake Delay

New features:
- No suggestions
- SRS Indicator in reviews
- HW Acceleration in reviews and lessons
- Mute Button