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>
Merge branch 'master' into issue-37
Allow platform specific Busybox customizations

Fixed apply-config-patch to exit successfully if platform
specific config options are not defined.