Implement mpm_itk on Debian

added what needed to have mpm-itk working on Debian based systems.
Fix failing system spec test
fix failing system specs reported in #347
Merge pull request #347 from blkperl/fix_system_test

Fix failing system spec test
Fix apache::default_mods loading

PR #314 was merged without tests and consequently had bugs. This moves
the `apache::default_mods::load` defined resource into
`manifests/default_mods/load.pp` and adds the missing `mods` parameter
to the `apache::default_mods` class. Also lots of tests are added.
Merge pull request #348 from hunner/fix_314

Fix apache::default_mods loading
Merge pull request #304 from kumy/itk

Add stuff to use ITK on Debian