Add version headers to distributed library files

**I'm submitting a feature request**

* **Library Version:**
doesn't matter

**Please tell us about your environment:**
Environment doesn't matter here

**Current behavior:**
There is no way to find out which specific version of a aurelia library file is used in an application.

**Expected/desired behavior:**
Add a short version header to each distributed file of all aurelia libraries.
E.g: `/* aurelia-bootstrapper 2.0.0; https://aurelia.io/ */` Or something similar to this.

**What is the motivation / use case for changing the behavior?**
An information like this is needed if your application does not use the library files directly from node_modules. In some of my projects I copy the needed files to another directory and push them to git (Reason for this is, because I want to have full control about version updates). This problem can be resolved with three solutions:
- A version header is included in each file (like described above)
- I have to copy the `package.json` files of each npm module to the corresponding location in my project directory.
- I have to remove version range characters in my `package.json` to avoid implicit updates in node_modules. But this only affects top-level dependencies.