Fix and update ActionBar icons for Night mode.

Also:
- Modified the convert script to pass each png through pngcrush, saving
  about 130KB from the total APK size.
- Modified the color and opacity of ActionBar SVGs to comply with Android
  design guidelines, and have consistent colors in History, Saved Pages,
  Main activity, etc.
- Removed SVG for the hamburger icon.
- Committing all updated PNGs that were affected by this.

Change-Id: I1b22a11ee57b489d013c75a7eee0b2b76d7eb98b