Adds an environment variable DIB_ADD_APT_KEYS pointing to a folder of
apt repo GPG keys. Each key will be verified and installed with apt-key
to the apt keyring.
Change-Id: I4b15347a76aa3241e741931bb94f17598641ae42
This includes the install-packages implementation for dpkg, apt http proxy
config, daemon blocking and unblocking.
Change-Id: I8f159021d2b223d7003cec067de3aa605ad06974