verhelp tikfoutje
Add Dir Both where we want an arrow tail + Remove NoArrow tails

Apparently it's a graphviz 'feature' to not draw arrow tails unless 'Dir Both' is specified.
Compute aggregations
Use aggChild/aggParent instead of aggSrc/aggTgt
Disable aggregates

We first need to establish the correct conditions that determine whether a relation is an aggregate. With the currently implemented conditions, some relations that are clearly not aggregates will nevertheless be considered as such.
Merge pull request #15 from AmpersandTarski/show-aggregations-in-logical-data-model

Show aggregations in logical data model

Code is currently disabled.
Use --test for interface documentation
First version of documentation for messages

(Add "CLASS Message" after an interface name to classify it as a message interface) @stefjoosten: expression and definition will probably not both fit in the table, so we have to make a choice or think of some other presentation.
Only create messages chapter if there are message interfaces
Show interface name in message table in bold