Rework docker build process

[Diokuz]

DO NOT MERGE

What was done

Rework dockerfile

1. Copy only production needed stuff
2. Install only production packages
3. Remove all caches
4. Move some packages to devDeps

The result is: decrease image size from ~400 mb to ~100 mb. 4x.

Requirements

1. This pr requires some changes on CI servers: .npmrc-docker file with auth token. So, for now it must not be merger. See readme.md in this pr for details.
2. Docker 1.13+ (2016 december version or higher). No need for --squash now.

[Diokuz]

I suddenly realized, that production packages are only koa and maybe superagent?.. anyway, 90% of "production" packages are actually not since we have no server side render.

I think that also will eliminate the need of auth. Gonna figure that out and rework pr.

[Diokuz]

Looks like moving deps decreased the size even further: to 100 mb, which is 4x times smaller! It'll be even better (I think ~80 mb) when yarn will fix its --production issue.

Also, because of yarn it is impossible to get rid of authToken, even if wings now in devDeps. yarn --production always tries to resolve all packages. Issue.

[narma]

LGTM

[eugene-sy]

If we update docker image base version here, can we do it for all our node projects?

[mbektimirov]

@jmataya Can you create new npm user to use its token for CI builds?

[eugene-sy]

I'd suggest using one COPY command for all files to reduce number of layers in the image.