Explicitely check transition conditions for follow up transitions and allow processes to have empty starting dialogs.

[svenoe]

We are enhancing how processes can be used with this comparatively small change significantly. Basically after a transition is completed, it will be explicitly checked, whether the conditions for the next transition are also fulfilled already and if so, it will be executed. This requires conscious setup of the processes, but it enables the admin to set up transition chains with various entry points, or optional acitvity dialogs, which will be skipped, if the information they provide is already present.

With this and also because it is needed to start processes via generic agent following CustomerTicketMessage, having activities without activity dialogs, and also having processes without starting activity dialog is not considered to be an error anymore.

[svenoe]

Basic functionality is implemented. Maybe some visual improvements or so will still come, closing the issue for now, though.