make createImageBitmap detection configurable

[wouterlucas]

With #456 we've introduced a finger printing mechanism to detect which API of createImageBitmap we support, this however introduced delays when starting the renderer.

Suggestion is to:

• Add createImageBitmap API flag
• Have an auto detect flag to still use the finger printing as introduced with Fixes for Chrome v38 #456
• Add variables for no options, options and cropping (or full) support of the API
• Set default to options (middle ground)
• Skip auto detection if a direct API directive has been provided

[wouterlucas]

completed in #526