Enhance Lane description in docs

Title: Lanes

Describe the issue:
The current description of the Lanes behaviour:

"In Process Designer, if a Element with the Actors or GroupID property defined, any new Elements defined in the Lane adopt the property values automatically."

is a bit misleading - both me and customer had different expectations about the runtime behaviour of Lane/Tasks after reading this docs.

I have created a KCS with detailed explanation of Lanes/Tasks which might serve you as a good starting point

https://access.redhat.com/solutions/1212653

Maybe even some actual screenshot of process definition including Lane/Tasks might be useful.