common: create DEB and RPM repository containing pulse2 agents

New script create-repos.sh transforms folders deb/ and rpm/
to repositories.
RPM repository includes the GPG signing process.
(TODO for DEB...)

Debian repository URL:
deb http://pulse2-server-url/downloads/deb ./

RPM repository URL:
http://pulse2-server-url/downloads/rpm

New dependencies:
- createrepo
- expect
- rng-utils