Bug 1499092 - rename/move code from 'feeds' and 'web content' to more appropriate/obvious versions for registerProtocolHandler, r=nika

Differential Revision: https://phabricator.services.mozilla.com/D13699

--HG--
rename : browser/components/feeds/WebContentConverter.js => browser/components/protocolhandler/WebProtocolHandlerRegistrar.js
rename : browser/components/feeds/moz.build => browser/components/protocolhandler/moz.build
rename : browser/components/feeds/test/.eslintrc.js => browser/components/protocolhandler/test/.eslintrc.js
rename : browser/components/feeds/test/browser/.eslintrc.js => browser/components/protocolhandler/test/browser/.eslintrc.js
rename : browser/components/feeds/test/browser/browser.ini => browser/components/protocolhandler/test/browser/browser.ini
rename : browser/components/feeds/test/browser/browser_registerProtocolHandler_notification.html => browser/components/protocolhandler/test/browser/browser_registerProtocolHandler_notification.html
rename : browser/components/feeds/test/browser/browser_registerProtocolHandler_notification.js => browser/components/protocolhandler/test/browser/browser_registerProtocolHandler_notification.js
rename : browser/components/feeds/test/mochitest.ini => browser/components/protocolhandler/test/mochitest.ini
rename : browser/components/feeds/test/test_registerHandler.html => browser/components/protocolhandler/test/test_registerHandler.html
rename : browser/components/feeds/test/test_registerHandler_disabled.html => browser/components/protocolhandler/test/test_registerHandler_disabled.html
rename : dom/interfaces/sidebar/nsIWebContentHandlerRegistrar.idl => dom/interfaces/sidebar/nsIWebProtocolHandlerRegistrar.idl
extra : moz-landing-system : lando