vue-cli Express plugin

Currently a replication for vue-cli#.

Will later be (most likely) turned into a more useful vue-cli plugin that will include Express with some nice best-practices covered:

• Logging (winston & morgan)
• helmet for security headers
• helmet-csp for Content-Security Policies
• session store (redis or file-based)

Every feature is opt-in.

TODO:

• Add a prompt for what to use as Express session store (file vs redis for example)
• Remove inlining of webpack manifest chunk (see this issue)
• Add app name and description to manifest.json of interface plugin dynamically based on global prompts/options
• Create logger helper