Add setenv/setenvif to apache::vhost

`SetEnv` is used by httpd to set environment variables for vhosts.
`SetEnvIf` is used to conditionally set environment variables.
Add optional purge parameter

Configuration of Apache should be managed by Puppet, as unexpected failures
can happen from erroniously placed configuration files. But in some
cases it may be desired to disable full puppet management for the time
being, and this `purge_configs` parameter will allow that to be
disabled.
Correct vhost_ssl.pp
Add priority to default ssl
Adding default_vhost true/false param

Any unmatched virtualhost requests are served by httpd to the
virtualhost configuration that was loaded first. Previously the
`priority` param was used to control `apache::vhost` loading order.

This commit adds a `default_vhost` parameter that should be used instead
of the `priority` parameter, and the priority parameter is only used in
specific cases when specific vhost loading order is required (which
currently do not exist, but may).
Merge pull request #7 from hunner/default_vhost_param

Adding default_vhost true/false param
Merge pull request #4 from hunner/add_setenv

Add setenv/setenvif to apache::vhost
Merge pull request #5 from hunner/optional_purge

Add optional purge parameter
Rename apache::mod::default to apache::default_mods

Similar to `apache::mod::dev` being moved to `apache::dev`,
`apache::mod::default` is not a module itself, just a collection of
httpd modules and so shouldn't exist in the `apache::mod::*` namespace.
Merge pull request #8 from hunner/rename_default_mods

Rename apache::mod::default to apache::default_mods
Merge branch 'refactor_module' of git://github.com/hunner/puppetlabs-apache into dynaguppy_hunner