* use ES6 import / export
* UTILS: export individual utilities
* TESTS: localize TestHelper includes
BREAKING CHANGE:
* all utilities export independent functions
* library sources got ported to ES6. You must now use
a ES module bundler such as Browserify + babelify or
Webpack to consume this library (or parts of it).
This commit puts all import related stuff into the import module.
The core module remains as an entry point to require the basic modules
needed by bpmn-js. At the time this is { import, draw }.