* fill, stroke, width and height can be overridden
* no other attributes can be overridden
* public API only exposes renderers for actual BPMN elements
Closes#1990
In the diagram `di` is now accessed via the diagram element, not the
business object. This has the benefit that elements in multiple diagrams
can easily be represented.
Related to https://github.com/bpmn-io/bpmn-js/issues/1472
BREAKING CHANGE:
* Instead of referencing the `di` from the business object, reference it
from the diagram element representing it.
* 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).
