Add support for Visual Studio Team Explorer 2017

[jcansdale]

From the Visual Studio website:

"Visual Studio Team Explorer 2017 is a rich, standalone client for accessing Team Foundation Server and Visual Studio Team Services and is free for any user. This install only includes Team Explorer so you can access version control and work item tracking without other IDE components."
https://www.visualstudio.com/en-us/news/releasenotes/vs2017-relnotes#te

At the very least, adding support for this could be useful for testing (a minimal install of VS with just the packages we need). It's also an obvious target for our extension!

At the moment all this PR does is allows the extension to load when the InstallationTarget is "Microsoft.VisualStudio.IntegratedShell".

We will likely want to check what components are available when loading the extension so we don't fail in any IntegratedShells that don't have Team Explorer available.

Fixes#938

[jcansdale]

I've added a dependency on the TeamExplorer extension (versions 14.0-15.*). This stops the VSIX Installer for showing it as an option for any instance of VS/VS Shell that doesn't have TeamExplorer installed.

This is probably a good independently of Visual Studio Team Explorer, in case someone doesn't have TeamExplorer installed in Visual Studio.

[jcansdale]

Not sure what else there is to do here. It's a simple change and seems to work as hoped. 😄

I wasn't completely sure which version range to use. I've plumped for [14.0,16.0) in case a new 15.x point release came out.

I notice we've used [14.0,15.0] in other places. Is this by design? Are we deliberately being pessimistic about compatibility with new point releases? Microsoft do have a "15.1" update out, but they seem to have kept the VS version at 15.0. 😕

[grokys]

This looks to be pretty low-impact.

The only thing I'd like to know is what version the usage tracker picks up here as it'd be good to have metrics on how many people use this.

[jcansdale]

I can't open PRs in some repos. There were some null ref exceptions, e.g:

Not sure if it's related to this PR. Need to investigate further.

[meaghanlewis]

@jcansdale earlier today I got the same errors with PRs in certain repos while using the latest master build so I don't think what you're seeing is related to this PR.

I was going to open up an issue about it, but then I logged out and back in again and haven't reproduced this problem since.

[jcansdale]

@meaghanlewis.

I got the same errors with PRs in certain repos while using the latest master build so I don't think what you're seeing is related to this PR.

Ah, thanks for letting me know! Will you open an issue about it? You can use the screenshot above.