Support an execution timeout for rules

[obfischer]

In case of an slow machine, a large database or an inefficient Cypher query, the query execution could take quit a long time. In such condition for the end user it is not clear if jQA hangs or the execution of the query simply takes a long time.

For such cases I would like to have the ability to define an execution timeout. If the execution of a rule takes more time than allowed jQAssistant should fail.