[ProcessDefinition option] Run All Startable Activities option

[jinyoung]

Currently, uEngine5 runs all the startable activities which are the first found activities. Start activities can be all the activities that doesn't have previous activity any more.

If designer wants to run only the activities which are connected after a StartEvent, this options stands for that intent.

[jinyoung]

Implemented engine part,

40559f5

We need to do more:

• Provides an user interface for input the option (maybe popup panel like process variable panel)
• Only the first level FlowActivity must be affected by the option. If not, since normal designers eager to define activities without StartEvent in a sub-process, this will stops running processes in the subprocess too.