Add self-documenting support

The primary builder will now generate a rule to call itself with
--docs=.bootstrap/docs/<name>.html to produce an automatically
generated documentation file.

The documentation generation process is:
 - Call each factory once to get empty property structs associated
   with the module type
 - Use reflection to determine the names of the type of each property
   struct
 - Use the bootstrap_go_package modules from reading the Blueprints files
   to find the source files for each Go package used to build the primary
   builder
 - Use the go/parser module to find the type declaration for each
   property struct
 - Extract comments for the property struct and each property declaration
 - Format all the comments into HTML

Change-Id: Icae9307cc10549a30bfc14d6922824099de5a9b0