Add apache::conf_dir, use it instead of params.

This is another change needed to make the httpd24 Software Collection
work on RHELish boxes.

Fix mod_systemd on RHEL/CentOS 6.

Puppet < 3.0 does not have unless.

Try another fix for Puppet 2.7 / Facter 1.7.

Add README and tests for ::apache::conf_dir.
Apparently missed one of these in the conversion

Use Concat instead of File.
Merge pull request #831 from mhaskel/typo

Apparently missed one of these in the conversion
Merge pull request #821 from smerrill/feature/fix-remaining-rhel6-scl-issues

Finish SCL support for RHEL/CentOS 6
Allow multiple balancermembers with the same url

Currently you can't set multiple balancermembers with the same url even
if they are bind to different balancers.

This commit fixes that unwanted behaviour.