* add <elements.create> rule for creating multiple elements
* handle creating multiple elements in CreateParticipantBehavior
* create sub process with start event through palette
* 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).
Related to bpmn-io/diagram-js#107
BREAKING CHANGE:
* Modeling#moveShapes got renamed to Modeling#moveElements
* Id of command changed from 'shapes.move' to 'elements.move'