Adapt 'enabled' to 'disabled' and emit a deprecation warning

In order to avoid the 'enabled' property we adapt it to 'disabled' (only
if 'disabled' is not already defined).

Also, it emits a warning in the console about this deprecated property
and its replacement.

Author: Martin D'Aloia

lib/rules.js

@@ -14,12 +14,15 @@ const createNewRules = (rules, rulesetDocumentationUrl) => {
 };
 
 const createNewRule = (rule, rulesetDocumentationUrl) => {
-    if (rule.disabled === true) {
-        delete activeRules[rule.name];
-        return;
-    }
     // @DEPRECATED in v0.9.0, use `disabled: true`
-    if (rule.enabled === false) {
+    if (rule.enabled !== undefined) {
+        console.warn("WARNING: Property 'enabled' is deprecated and will be removed in 1.0.0. Use 'disabled' instead. Found in rule: " + rule.name)
+    }
+    if (rule.enabled === false && rule.disabled === undefined) {
+        rule.disabled = true;
+    }
+
+    if (rule.disabled === true) {
         delete activeRules[rule.name];
         return;
     }