Get emmet completions from css extension (#41652)

* Get emmet completions from html,css extensions

* Resolve extensionsPath, use emmet results even if empty

* Support css abbr with :

* Refactoring

* Add some basic emmet tests

* Refactoring

* More tests

extensions/html/package.json

@@ -73,10 +73,12 @@
         "end": "^\\s*<!--\\s*#endregion\\b\\s*(.*?)-->/"
       }
     },
-		"snippets": [{
-			"language": "html",
-			"path": "./snippets/html.snippets.json"
-		}],
+    "snippets": [
+      {
+        "language": "html",
+        "path": "./snippets/html.snippets.json"
+      }
+    ],
     "configuration": {
       "id": "html",
       "order": 20,
@@ -225,10 +227,10 @@
   },
   "dependencies": {
     "vscode-extension-telemetry": "0.0.11",
-    "vscode-languageclient": "^3.5.0",
+    "vscode-languageclient": "^4.0.0-next.8",
     "vscode-nls": "^3.2.1"
   },
   "devDependencies": {
     "@types/node": "7.0.43"
   }
-}
+}