Use Epol EpollEventLoopGroup if supported by OS

[hamadodene]

#415

EpollEventLoopGroup vs. NioEventLoopGroupand in high load scenarios could provide better performance in:

• CPU usage
• Memory usage
• Allocations

It would be good to include the ability to switch to EpollEventLoopGroup if the operating system supports it.

For listener- example:

listener.1.keepalive=true|false 
listener.1.keepaliveidle=300
listener.1.keepaliveinterval=60
listener.1.keepalivecount=8
listener.1.maxkeepaliverequests=1000

[hamadodene]

@pv3nturi @NiccoMlt I also made the keepAlive options configurable.
Added keepAlive options on server side as well.

[pv3ntur1]

LGTM but you'd better to add a few tests to check for property names typo.

[pv3ntur1]

+1