This renames the classes and defined types from apache to httpd.
With the 'httpd' module available, we can migrate usage of 'apache'
to 'httpd.' Eventually this will free the 'apache' namespace.
A native ruby type and provider is contained in this class. It is
not namespaced to the class name so it has been renamed from a2mod
Previous to this comit, the a2enmod and a2dismod commands were required
for the a2mod provider to be used by puppet on the first run. Since
these commands are not always available on the first run, the catalog
application might fail. This commit makes the commands optional, so the
provider's validity will be evaluated when an a2mod resource is enforced
Previous to this commit, the `a2mod type did not autorequire the
Package['httpd'] resource provided by the `apache` class. If the
Package['httpd'] resource was enforced after any a2mod resources, the
a2mod resources would fail since the httpd package installs the
a2emod/a2dismod system commands.