Allow configuration for base path to request asset files. #6121

Bug Report or Feature Request (mark with an x)

- [ ] bug report -> please search issues before submitting
- [x] feature request

Versions.

@angular/cli: 1.0.1 .
node: 7.5.0 .
os: darwin x64

Repro steps.

My build target is in ./public/assets directory. The generated files (*.js, *.js.map, index.html) all go into that directory. When the files are generated the script tag urls are like so: http://example.com/file.js

Desired functionality.

I need the script tag urls to be http://example.com/assets/file.js. Notice the /assets/. This is because public is the web root and I'm serving index.html through my backend application. Therefore, when they hit http://example.com, index.html is served even though it's in http://example.com/assets/index.html. I apologize if this is confusing, please ask for clarification if needed.

Mention any other details that might be useful.

http://github.com/jaesung2061/anvel

I currently have it so that the index.php, .htaccess and other files are copied from the angular src directory. Because of #4293