chore(project): add eclipse specific .gitignore
feat(product): add branded product

This commit adds a kepler based branded camunda Modeler product.

Contained is

* Styling of spash screen / about / icons
* Customization `modeler` launcher
* Cross platform build support (via product)

Along with https://app.camunda.com/jira/browse/CAM-1648 this enables
direct opening of files from the file system, too.

Closes #4
Closes #5
Closes #6