[RFC] Support for copying non-JavaScript files to the instrument command output directory

## Problem

Currently `instrument` command only instruments and copies JavaScript files to the output directory. Other non-JavaScript files are left as is and aren't copied over.

A lot of times you also store other files in the same directory as you store JavaScript source files (think fixture files, assets, etc.) and  JavaScript source files include those resources based on a relative path.

In this scenario, if you want to execute instrument code, you also need to copy all the non JavaScript files to the `instrument` command output directory.

## Proposed Solution

This pull request adds `--[no-]complete-copy` flag to the instrument command. If this flag is true it will copy other (non-JavaScript files) as it to the instrument command output directory.

For backward compatibility reasons I've set default value to false.

Feedback is welcome.