Update several third_party libs:
* guava 15 -> 18
* soy to latest revision (see read me)
* icu4j 4.8.1.1 -> 51.1
Replace use of deprecated constructor.
Replace org.json with com.google.gson
Inject FileSystem throughout so I can start using jimfs to write tests against
the generated docs.
Upgrade to protobuf 2.5.0 and closure-compiler v20141023
Fix to work with injected file systems.
Simplify module type handling by converting CommonJS modules to Closure's
goog.module syntax.
Update closure_library
Remove debug print statements
Update intellij project so closure_library is available.
Simplify type resolution
Delete unused file.
Preserve template type expressions when generating the link to another type.
Fix type expression parsing.

* Remove extra = suffix on optional function parameters.
* Remove unnecessary . before template type expressions.
Omit empty links
Fix details & summary element polyfill detection logic (hasOwnProperty('open')
returns false for details elements on Safari)
When printing template types in a file header
a) drop the unnecessary "." prefix before the template
b) don't code format
Fix module processing now that we're using goog.module transformations.
Rewrite module.exports references to the exports free variable.
When collecting types for the class inheritance tree, don't generate a link to
the leaf type.