docs(versions): provide version menu for navigating to versioned docs

[radamant]

This was created in collaboration with @marcysutton.

Refs #918 provides version menu (with customizable minimum-version cutoff)
that navigates to docs based on a simple string format.

This approach was based on that provided in the base angular.js repo,
and some of the code was ported from that repo.

It looks like this:

As aforementioned, this works pretty much identically to the one in the angular.js repo, using much of the same code. It gets previous version from the list of tags, and adds a CDN and snapshotted version if available. The doc url generation is controlled by two variables, one to determine the minimum version for which doc urls will be generated, the other to format of the URL for versioned docs (none of the URLs currently exist.)

I do not have access to either material's public-facing servers nor its CI configuration(s), so there are still several items that must be done before this can be rolled out:

• determine where snapshotted versions will be hosted, angular currently uses https://code.angularjs.org/:version:/ which is why this PR uses https://code.angularjs.org/material/:version/.
• provide documentation for older versions (or just set the min-version to >=0.8.3 and start with the current version)
• add the version processor, controller and template to the docs for any older versions that should go in the version list
• test with a real snapshotted version (I have only tested with a "-local" version on my machine)
• @marcysutton to work on fixing the accessibility for the labels of md-select -> mdSelect: accessibility label lost when item is selected #1893

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[radamant]

@googlebot CLA is signed.

[googlebot]

CLAs look good, thanks!

[ThomasBurleson]

@marcysutton - this PR is incomplete due to dependent features:

• determine where snapshotted versions will be hosted, angular currently uses https://code.angularjs.org/:version:/ which is why this PR uses https://code.angularjs.org/material/:version/.
• provide documentation for older versions (or just set the min-version to >=0.8.3 and start with the current version)
• add the version processor, controller and template to the docs for any older versions that should go in the version list
• test with a real snapshotted version (I have only tested with a "-local" version on my machine)
• @marcysutton to work on fixing the accessibility for the labels of md-select -> mdSelect: accessibility label lost when item is selected #1893

@robertmesserle - can you and I work with BrianF to prepare these above items for 0.9 release?

[ThomasBurleson]

Closed. See SHA 57e9ea4