Bug 40926: Implemented the New Identity feature

browser/base/content/appmenu-viewcache.inc.xhtml

browser/base/content/browser-init.js

browser/base/content/browser-menubar.inc

browser/base/content/browser-sets.inc

browser/base/content/browser.js

browser/base/content/navigator-toolbox.inc.xhtml

browser/components/moz.build

browser/components/newidentity/content/newIdentityDialog.css

browser/components/newidentity/content/newIdentityDialog.js

...er/components/newidentity/content/newIdentityDialog.xhtml

browser/components/newidentity/content/newidentity.js

browser/components/newidentity/jar.mn

browser/components/newidentity/moz.build

browser/modules/BrowserWindowTracker.sys.mjs

browser/themes/shared/icons/new_identity.svg

browser/themes/shared/jar.inc.mn

browser/themes/shared/toolbarbutton-icons.css