feat(locators): add toString() wrapper for this.message
docs(contributing): consolidate contributing docs

Now, all in CONTRIBUTING.md
chore(dgeni): moving doc generation to its own folder

Now the docs/ folder is purely documentation, and the docgen folder contains all
configuration and templates.
cleanup(docs): move reference configuration into docs folder
feat(protractor): implement reduce and filter for ElementArrayFinder

See https://github.com/angular/protractor/issues/877
fix(launcher): report summary when specs fail