Restructure to allow root entry and correct sub directory entry paths

We can now have a root entry point at the same time as having a sub directory entry points.

### Here are the highlights of the changes
* Fixes the relative paths to file loader assets no matter where the entry point is in the path
* An absolute path will be used for the `webpack-dev-server`
* Relative paths will be used if wanted by default in the `webpack` build into `/dist`
* A public relative path is created based on the entry point context rather than absolute from root context
* Added the boilerplate example with both one root and one sub directory entry point
* It will allow for any number of levels deep in the directory structure
* Each entry point can now be saved as it's own module and will install to any virtual path if all file-loader assets are relative to the entry

### Notes:
I believe there should be a fix to the file-loader as in my fork here [talves/file-loader](https://github.com/talves/file-loader/compare/webpack:master...master) to make sure url paths end up in a more direct relative path to the index.html entry point. (i.e. images/... vs ../boilerplate/images/...) by using the root context (context + /boilerplate) to resolve the url path.
The change is not required, but allows us to have a stand alone entry path without having to be dependent on the public path being set in the [resource file](https://github.com/talves/famous-webpack-seed/blob/master/src/boilerplate/resources.js#L1) in the file loader.  

In the current solution, we will not be able to export a module to just any path if we do not use the new file-loader changes.