Re-factored database.rake to allow Jdbcpostgresql. #jruby

RDoc autolinks the word "Rails" to the doc page for the Rails module.
But README.rdoc is displayed in the home page at GitHub and the slashes
are visible there, which is weird. We leave by now the slashes off in
the file, and generate a second file for the API with them.

Conflicts:
	railties/guides/source/contributing_to_ruby_on_rails.textile

Prototype and Scriptaculous are no longer vendored, but provided by prototype-rails from now on, also the -j option of the application generator is removed

Removed so info about assigning to specific devs and adding tags.  I don't believe that you can do that in GitHub issues.  Remove state:committed notes as they also don't exist in GitHub issues.

* outlines how to review pull requests
* outlines how to issue pull requests
* changed all references from LH => GH

Fixed documentation, 'asset' -> 'assets'