DAB Engine Cosmos Improvement : Given key 'x' was not present in the dicitonary

[sajeetharan]

Engine should throw a valid error to the user regarding the configuration file.

Scenario : If user does not have entities in the entities section and run the engine. It throws an error as
"Given key 'x' was not present in the dicitonary"

Expected result : It should give a proper error saying the entities are not present in the configuration file or something.