chore(project): cleanup dependencies
chore(examples): remove from repo

Examples now reside in their own repository:

https://github.com/bpmn-io/bpmn-js-examples
fix(importer): import label on messageFlows

Closes #76
fix(import): hide labels of hidden elements

Closes #78
chore(modeler/viewer): clean up module loading + api
chore(util): introduce Di utility
feat(test-environment): add diagram-js like test env
feat(label-editing): edit all labels

Related to #7