Jenkins: Add LXC execution script
Jenkins: Set up 'base' job for LXC-based execution

 * Don't install unused packages
 * Remove 'install dev env' step from 'base'
 * Add opam dep installation script to base
 * Set script interpreter
 * Use pre-installed opam
 * Turn absolute symlinks created by ocamlbuild into relative

   Since the workspace is bind-mounted inside a container, but Jenkins
   runs outside the container, it can't handle absolute symlinks inside
   the workspace.

   'ocamlbuild' creates absolute symlinks though when building something.

   This commit fixes this by using 'symlink -c' to turn the absolute links
   inside the workspace root into relative ones.

 * Set 'seed' for 'base' job
Jenkins: Set up 'system_tests_quick' job for LXC-based execution

 * Remove all 'sudo' calls from system_tests_quick
 * Add interpreters to system_tests_quick scripts
 * Remove 'install sandbox' script from system_tests_quick

   A sandbox image is pre-installed in the seed.

 * Use pre-installed 'opam'
 * Add 'seed' to system_tests_quick
Jenkins: De-sudo'ify buildInSandbox.sh
Tests: Run 'iptables' with 'sudo'
Jenkins: Set up 'system_tests_slow_left' job for LXC-based execution

 * Remove 'install sandbox' step from system_tests_slow_left
 * Add interpreter lines to system_tests_slow_left scripts
 * Remove 'sudo' usage from system_tests_slow_left
 * Add 'seed' file to system_tests_slow_left
Jenkins: Set up 'system_tests_slow_right' job for LXC-based execution

 * Remove 'install sandbox' step from system_tests_slow_right
 * Add interpreter lines to system_tests_slow_right scripts
 * Remove 'sudo' usage from system_tests_slow_right
 * sudo'ify 'iptables' calls in system_tests_slow_right
 * Add 'seed' file to system_tests_slow_right
Merge pull request #13 from Incubaid/jenkins-lxc-for-1.6

Jenkins: Use LXC containers