Improve the image editor.

A variety of improvements to the image editor, such as:

- New, fullscreen styling
- Smoother lines
- Better text and sticker handling
- Improved color picker with a history pallette
- New highlighter tool

res/drawable/circle_white.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval">
+    <solid android:color="@color/white"/>
+</shape>