Major refactoring of cookbook as part of work w/ MSFT Open Technologies Office.

Major changes:

* Rename cookbook to apache_windows from apache-windows, so that LWRPs work properly
* Use generic HTTPD build from Apache Software Foundation
* Manage config files as close as possible to the vendor distribution. As such, this
  cookbook does not install a2[en,dis]site or any other Ubuntu-style utilities
* Include unit tests in ChefSpec.