Add all-in-one build target

Added an all-in-one target that puts the the system and user data all
on a single disk image. Could be useful in cases where your cloud
provider has very large root disks and you don't need the ability to
periodically reset the VM to the gold state while retaining user data.

Note for the future: editdisklbl can't handle creating images with
extended partitions. Fortunately we can get away with just the 4
standard, non-extended partitions.

Change-Id: I77e015dc6a8f6b9753d9ba7bd59a463f94619344
Massive build-script rewrite and prettification

Overhauled the build-svmp2.sh script to support all the new features
that will be getting added to the build system.

* Graphical menus for picking options
* Saves configuration to a file for future reuse
* Only builds the images the user actually wants, not everything
* Simplified the image format conversion rules

Change-Id: I5184de9d6f00e1dcc8e5cfe59060d20cde20c239