(MODULES-1457) apache::vhost: SSLCACertificatePath can't be unset

The SSLCACertificatePath is always set. The check for @ssl_certs_dir only
covers "undef". As there is a default value in ::apache::params for
ssl_certs_dir it needs to be overriden with an empty string.

Right now the _ssl.erb template outputs 'SSLCACertificatePath ""' for an empty
string, which triggers a failing reload of httpd.

This patch just adds a "&& @ssl_certs_dir != ''" to the condition.

On a Puppet master passenger vhost it's probably  security relevant setting,
as it enables all system CA signed certificates access.

Related patch: https://github.com/puppetlabs/puppetlabs-apache/pull/787
Added ssl_protocol parameter to apache::mod::ssl

makes it easier to fix things like POODLE
fix ssl_protocol docs to be in line with code
Satisfy doesn't work with apache 2.4

The ability to use the more complex Require* syntax for apache 2.4
will be added eventually, but Satisfy shouldn't be tested as that is
deprecated in apache.
wsgi_chunked_request doesn't work on lucid
Update metadata

Fix PE compatibility, update issues URL, and fix requirements to match
output from PMT.
Ensure balancer config is written to correct location

Balancer configuration is written to wrong directory if custom confd_dir
is passed to Apache.

Change Concat resource to use `$::apache::confd_dir` rather than
`$::apache::params::confd_dir`.

This is required for httpd24 (RHEL/CentOS 6.5) which uses
`/opt/rh/httpd24/root/etc` for configuration.
Remove <IfModule ...> checks as the configuration within the system should be known with respect to the proxy and disk cache modules being loaded. This change also helps because the module name changed in Apache 2.4 from mod_disk_cache to mod_cache_disk, which would have required this template to become more complicated.
Change to determine the $cache_root variable and disk cache module to load depending on the version of Apache. In Apache 2.4 and later the module name changed from mod_disk_cache to mod_cache_disk and so did the location of the cache.

TODO: Determine whether the $cache_root location was also updated in FreeBSD.