Switch Jade to Pug

[mjbvz]

Jade had been renamed to Pug for legal reasons, so when a user creates an express project using our NTVS express templates, they end up seeing a warning about switching to use Pug instead of Jade.

We should:

• Update the project templates that use the latest version of Jade to use Pug instead. I think all of our templates use "jade": "*"
• Update any user facing strings.
• Update our documentation to make all this clear.

Not sure if the *.jade file extensions should be changed too. It's all rather confusing.

[mjbvz]

The point about the package.json templates using "jade": "*" is true for every template except ExpressApp4 and AzureExpressApp4.

[mjbvz]

I think they changed the extension too: pugjs/pug#2292 (comment)

We've decided to wait until pugjs/pug#2184 is finished before making this change, just to let things stabilize a bit more.