[Libguestfs] [PATCH] customize: Move virt-customize-related code to a separate

There's not going to be an easy way to present this patch. It's huge and interconnected. Anyway, what it does is lay the groundwork for a new tool which I'm calling 'virt-customize'. virt-customize is virt-builder, but without the part where it downloads a template from a respository. Just the part where it customizes the template, that is, installing packages, editing configuration files, setting a random seed and so on. This patch splits the customize bits of virt-builder out into a separate library (all the code under customize/). Eventually this subdirectory will evolve into a virt-customize tool, and virt-sysprep will also use the library. But in the current patch the library is only used in virt-builder. Mostly this is painful code motion. Rich.