No need to source /etc/jenkins/debian-glue twice in the same script
generate-git-snapshot: Support PRE_DCH_HOOK variable for custom scripts

This allows stuff like:

  echo "sed -i 's/^Section: _SECTION_/Section: dev/' debian/control" > /tmp/changeVersion.sh
  export PRE_DCH_HOOK="/tmp/changeVersion.sh"
  /usr/bin/generate-git-snapshot

Thanks: Rudolph Bott <bott@sipgate.de> for the patch
Introduce REPO_CODENAME variable. Value is distribution when building release package, same behaviour as now in other case
Introduce REPO_CODENAME variable in build-and-provide-package. Value is distribution when building release package, same behaviour as now in other case
Removed useless SUDO_CMD. Add REPOSITORY since we do not include /etc/jenkins/debian_glue any more in generate-reprepro-codename