XX-11224: Configure Edge Servers via YARD

-new gateway plugin (Edge Server)
rest calls to get YARD properties and to save YARD properties
-extend EditGateway page to display gateways without Dial Plan or Caller id tabs
Edge Server does not directly attach to Dial Plan
-2 tabs: Web Rtc properties settings and authentication settings for yard server (username and password
for the web rtc properties tab, the default values show the value actually stored in YARD (N/A if not existing)
-json to java POJO marshaling using Jackson api for get/save in YARD