olpc-os-builder config tweaks

[Daniel Drake]

Hi Chris,

I added a mechanism so that we can keep separate the OLPC-specific
configuration from the sample config that can be reused by
deployments, and I stripped out the OLPC-specific bits from those
default configs.

So you'll want to create a cjb-specific config file somewhere with
this contents:

[global]
official=1
modules_extra=signing

[signing]
bios_crypto_path=/home/cjb/git/bios-crypto
make_zsp_fs_zip=1


then when making builds, run the program with
--additional-defaults=/path/to/cjb-extras.ini

Daniel