Add recipe to install apache plugin with custom url.

At present, stackdriver doesn't pick up apache settings at least when you have a different mod status url.  

This recipe should provide users the ability to setup a apache plugin while installing stackdriver agent.

It does not enable mod-status module in apache however, That is left to the apache cookbook.  The plugin conf is take from here: http://feedback.stackdriver.com/knowledgebase/articles/232548-apache-plugin