feat(webdriver-manager): redo the script to run and install selenium/webdriver

Breaking Change.
As outlined in Issue #296, redoing the way the selenium/webdriver
install and run helper scripts work. Now, the 'webdriver-manager' script
will be available either locally or globally (depending on how protractor
was installed). It replaced install_selenium_standalone and the 'start' script
that was provided after install. Run `webdriver-manager update` to download
new versions of selected webdriver binaries. Run `webdriver-manager start`
to start the standalone server. In addition, this fixes issues with running
the server starter in Windows, and allows automated downloading of the IEDriver.

Thanks to kurthong and vipper for their PRs with windows fixes, which were
very useful in preparing this.
docs(install): update docs for the new webdriver-manager script