Add `page_title` attribute to each documentation file for which it didn't...

Add `page_title` attribute to each documentation file for which it didn't already exist, matching the value to each page's h1, respectively.

website/source/docs/basics/terminology.html.markdown

 ---
 layout: "docs"
+page_title: "Packer Terminology"
 ---
 
 # Packer Terminology

website/source/docs/builders/custom.html.markdown

 ---
 layout: "docs"
+page_title: "Custom Builder"
 ---
 
 # Custom Builder

website/source/docs/builders/digitalocean.html.markdown

 ---
 layout: "docs"
+page_title: "DigitalOcean Builder"
 ---
 
 # DigitalOcean Builder

website/source/docs/builders/docker.html.markdown

 ---
 layout: "docs"
+page_title: "Docker Builder"
 ---
 
 # Docker Builder

website/source/docs/builders/googlecompute.markdown

 ---
 layout: "docs"
+page_title: "Google Compute Builder"
 ---
 
 # Google Compute Builder

website/source/docs/builders/null.html.markdown

 ---
 layout: "docs"
+page_title: "Null Builder"
 ---
 
 # Null Builder

website/source/docs/builders/openstack.html.markdown

 ---
 layout: "docs"
+page_title: "OpenStack Builder"
 ---
 
 # OpenStack Builder

website/source/docs/builders/qemu.html.markdown

 ---
 layout: "docs"
+page_title: "QEMU Builder"
 ---
 
 # QEMU Builder

website/source/docs/command-line/introduction.html.markdown

 ---
 layout: "docs"
+page_title: "Packer Command-Line"
 ---
 
 # Packer Command-Line

website/source/docs/extend/command.html.markdown

 ---
 layout: "docs"
+page_title: "Custom Command Development"
 ---
 
 # Custom Command Development

website/source/docs/extend/developing-plugins.html.markdown

 ---
 layout: "docs"
+page_title: "Developing Plugins"
 ---
 
 # Developing Plugins

website/source/docs/extend/post-processor.html.markdown

 ---
 layout: "docs"
+page_title: "Custom Post-Processor Development"
 ---
 
 # Custom Post-Processor Development

website/source/docs/extend/provisioner.html.markdown

 ---
 layout: "docs"
+page_title: "Custom Provisioner Development"
 ---
 
 # Custom Provisioner Development

website/source/docs/index.html.markdown

 ---
 layout: "docs"
+page_title: "Packer Documentation"
 ---
 
 # Packer Documentation

website/source/docs/other/core-configuration.html.markdown

 ---
 layout: "docs"
+page_title: "Core Configuration"
 ---
 
 # Core Configuration

website/source/docs/other/debugging.html.markdown

 ---
 layout: "docs"
+page_title: "Debugging Packer"
 ---
 
 # Debugging Packer

website/source/docs/other/environmental-variables.html.markdown

 ---
 layout: "docs"
+page_title: "Environmental Variables for Packer"
 ---
 
 # Environmental Variables for Packer

website/source/docs/templates/builders.html.markdown

 ---
 layout: "docs"
+page_title: "Templates: Builders"
 ---
 
 # Templates: Builders

website/source/docs/templates/introduction.html.markdown

 ---
 layout: "docs"
+page_title: "Templates"
 ---
 
 # Templates

website/source/docs/templates/post-processors.html.markdown

 ---
 layout: "docs"
+page_title: "Templates: Post-Processors"
 ---
 
 # Templates: Post-Processors

website/source/docs/templates/provisioners.html.markdown

 ---
 layout: "docs"
+page_title: "Templates: Provisioners"
 ---
 
 # Templates: Provisioners