issues 367 and 406 - icons and splashes and hooks, oh my

#### (NOTE: these changes include adding a new npm package. Thus it requires a quick `npm install` before it'll work)

This is a few new images and a near total re-write of the versions hook

I had to move the config hook from before_prepare to after_prepare because some things like the package id were being clobbered by the prepare stage.

Then, because I did that, I have to move the versions hook as well, but since it was modifying config.xml prior to its use in the prepare stage, that method of modifying the version would no longer work.

Since I already HATED the way I had done that anyway (constantly modifying a file under git control), I decided a refactor was in order. I changed the versions hook to use the values from the config and modify each platform's config file in-situ after having been copied by the config hook.