added icons, splash screen and new hook

Added after_prepare hook to copy over IOS icons and splash screens as
well as Andriod icons.  Also updated config.xml to use new icons and
splash screens for phone gap build.
fixed typos in filestocopy array
updated android screenshots
Merge pull request #87 from rhoads-zach/master

added icons, splash screen and new hook. Verified by building locally with CLI and in PhoneGap Build based on branch