Modify default time source to take advantage of increased precision

Created by: wilaw

mediaplayerModel.js specifies the default time source as

const DEFAULT_UTC_TIMING_SOURCE = { scheme: 'urn:mpeg:dash:utc:http-xsdate:2014', value: 'http://time.akamai.com/?iso'

http://time.akamai.com/?iso returns an ISO timestamp looking like

2018-09-10T18:51:06Z

This iso time source is now available with millisecond precision, by appending the new query arg '&ms' to the request. So a request to http://time.akamai.com/?iso&ms will return

2018-09-10T18:51:06.214Z

Request is to change the default DEFAULT_UTC_TIMING_SOURCE value to 'https://time.akamai.com/?iso&ms'. Note that it may be necessary to escape the '&' character.

I also see some documentation references to "http://time.akamai.com/?iso" - these should be updated as well.

Cheers Will