Develop

Hi,

because I'm completely new to Eclipse plugin development I had some troubles setting up the camunda modeler using the Contribution guide.

Some problems were:

* BPMN 2.0 Meta-Model Update Site is wrong
* Tycho plugin is not installed automatically
* Graphiti must be installed and then updated to match the required version

Therefore I added a detailed "walk through" to help beginners with the setup.

I hope this helps.

Best regards,
Michael