Change ic_action_help to black, instead of gray.

This is not the default, but it just looks bad with (default) black
title text, and plenty of official google apps seems to change the
icons to be fully white or fully black.
Generated with:
http://romannurik.github.io/AndroidAssetStudio/icons-actionbar.html#source.type=clipart&source.space.trim=0&source.space.pad=0&source.clipart=res%2Fclipart%2Ficons%2Faction_help.svg&name=ic_action_help&theme=custom&color=000%2C100

I wish this the Material theme had better defaults and I wish this
was mentioned in the Material design guidelines.
ic_action_favorite: Make this black too.

Generated with:
http://romannurik.github.io/AndroidAssetStudio/icons-actionbar.html#source.type=clipart&source.space.trim=0&source.space.pad=0&source.clipart=res%2Fclipart%2Ficons%2Faction_favorite.svg&name=ic_action_favorite&theme=custom&color=000%2C100
ic_action_undo: Make this black too.

And also change it to the new (content_undo) icon for Material design,
though I don't like it as much.
Generated with:
http://romannurik.github.io/AndroidAssetStudio/icons-actionbar.html#source.type=clipart&source.space.trim=0&source.space.pad=0&source.clipart=res%2Fclipart%2Ficons%2Fcontent_undo.svg&name=ic_action_undo&theme=custom&color=000%2C100
ic_action_invert: Make this black too.

Generated from drawable/ic_action_invert.svg with:
http://romannurik.github.io/AndroidAssetStudio/icons-actionbar.html#source.type=image&source.space.trim=1&source.space.pad=0&name=ic_action_invert&theme=custom&color=000%2C100
ic_toolbar_icon: Make this black too.