Fix missing semicolon in dim level setting
Initial options page work

Show the user their current site customizations and offer a chance to
reset them all. Remove the dangerous button to reset all customizations
out of the popup.
Add option to disable high DPI workaround
Enable forcing hardware acceleration in options

Forcing the hardware accelerated rendering path with the backface
visibility style was formerly only used as the high DPI workaround. It
may have performance benefits as well, so it's helpful to be able to
force hardware acceleration.
Workaround for html background ending
Fix base64 encoded JPEGs

Resolves issue #57
Attempt to reduce white flicker before page load
Fix bad background color on browser reload
Add ribbon to highlight new options button
Remove "NEW" label from Dim setting in README
Fix issue parsing sitemodifiers on new installs
Fix error clearing site customizations
Reword option to force hardware rendering
Use JavaScript to do additional image discovery
Add experimental option to detect animated gifs

Disabled by default because it slows stuff down a lot.
Don't affect printing

Add the media="screen" attribute to the CSS link tag to prevent
inversion from affecting printed pages. It's almost never reasonable to
invert things for people printing.

Resolves Issue #54
Branch for release 0.6
Merge branch 'dev'

Changelog for release 0.6.0:
  * "Smart" mode got more smarter
  * New options page to control advanced settings and workarounds:
    - This is the new home of the "Forget Site Customizations" button,
      so it's not so easy to accidentally click during normal use.
    - Can now force or disable the hardware rendering path used as a
      workaround for high DPI blurriness.
    - Can enable a new experimental feature to uninvert animated GIFs in
      "Smart" mode.
  * Fix for full screen not being inverted on short pages.
  * Reduced white flicker in many situations.
  * Other minor fixes and cosmetic tweaks.