Clean publish and eject

Created by: Jiansen

• separate dev config and prod config, including paths.js
  • part of #191
• cleanup code on eject
  • same as in #206 , can close 206 if this PR is accepted.
  • as discussed in #206, the --smoke-test tag is kept in production code for now
• on release, only ship configurations for production code
  • in the node_module installed at users side, there will be no --debug-template flag
• same as above, in e2e test, when testing cli, only pack production code
• on local dev (i.e. build and start), use dev configuration

Disscussion 1: add parameter stage to pack.sh so that

• pack.sh prod only ship prod configurations
• pack.sh dev only ship dev configurations
• pack.sh test only ship test configurations
• etc.

This can be done by removing files in package.json, and creating a few versions of .npmignore files (e.g. .npmignore.prod).

Disscussion 2: further split paths.prod.js to 2 files, paths.beforeEject.js and paths.afterEject.js; remove the // Dead code on eject:start/end block.

Question: start.js always use the dev config for webpack. Is there a reason for this? In my local test, it seems fine to use production config in a generated app.