MULE-8013: Added connections configuration parameters for incoming and o...

...utgoing requests.
I have given feedback previously that using a boolean to enable/disable persistent connections has limitations, because when we add "maxPersistentConnections" (ideally before 3.6) which is required to tune performance for different types od scenario we end up with a situation where we have two attribute rather than one to confgure this with values that may conflict.  

The simple way to prevent this is to have a single integer attribute which is set to 0 if peristent connection shouldn't be used.