Add more options to diagram generation

[tsurdilo]

What would you like to be added: Add more options to diagram generation. Some ideas include

1. add option to display diagram vertically/horizontally
2. add option to define the min/max size of the generated diagram
3. add ability to display actions (service invocations)
4. add custom node representations for different states Why is this needed: to improve diagram generation

[manick02]

@tsurdilo Is this issue still relevant for me to pick it up?