Fix Issue 15816 Add exception if port range specified for discovery.zen.ping.unicast.hosts

[mortonsykes]

Added a regex expression to determine if a port range is specified in the config file, "elasiticsearch.yml" in the "config" folder of the built application. If this is the case an exception will be thrown as this is unsupported.

example: Contents of elasiticsearch.yml

.... 
discovery.zen.ping.unicast.hosts : ["128.0.0.1", "127.0.0.1:9000", "192.0.0.1:9200-9300"]
....

In this example the third entry "192.0.0.1:9200-9300" will cause the exception to be thrown.

upi: msyk659 group: Group 1

[nik9000]

It is usually a better choice to make the PR's title descriptive of what you are doing rather than a reference to an issue for a few reasons:

1. When I am looking over my email to see what to review I scan the email's subjects which are the titles of the PRs. I don't have all the issues memorized so if you reference an issue I'm not going to review it.
2. When you click the merge button you'll get a commit with the short description the same as the PR's title and it is much nicer to have descriptions instead of links in the title.

[StefanGor]

Code looks good to me.