Alpha Networks SNQ60A0_320F: Remove Demo OS partition work around

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Add more dependencies to debian-prepare-build-host target

Issue #39:
The following missing dependencies were added:

* libncurses5
* libncurses5-dev
* bc

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Allow platform specific Busybox customizations

Issue #37 - This commit adds support for customizing busybox
config on a per platform basis.

We're currently supporting only config customizations similar to
how its done for the kernel.

Custom configs can be placed under: machine/<platform>/busybox/config
and the build system will pick it from there.

The customizations are optional and the build system will use
existing defaults if its not defined by a platform.

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>