Fix #7 - Use contentful ID as node ID and escape special charaters for node labels

[Swissbite]

Fix #7 by implement update the way how a dot file is generated.

• Use the field sys.id for each content model as a node identifier.
• Escape the special characters <>\| in names for fields or the model

Additional:

• Ensure lint on tests and on import.js.
• Fix lint issues

[lotas]

that's a really huge contribution right here :) Thank you once again!