GH63: Adds Visual Studio 2017 support

[agc93]

There's a lot of changes here:

• Updated to VSIX v3 format
• Templates now need VSSDK build package to build correctly
• Move icons up one level so they are found by manifest search
• Update icons with correct inversion pixels
• Metadata updates

Resolves #63

[agc93]

Hey @cake-build/team someone good to have a look over this?

[yannduran]

Any news on this? I was about to start using cake, but I'm using VS 2017.

[garyng]

Any updates? 😄

[agc93]

@cake-build/cake-integrations someone want to have a look over this before merging?