Improve a bit Plesk-related things (#2445)

- Plesk-related headers values are always starting with "Plesk"
- Plesk can run on Windows
- Plesk's website is using https

src/apps.json

@@ -7524,12 +7524,12 @@
         9
       ],
       "headers": {
-        "X-Powered-By": "PleskLin",
+        "X-Powered-By": "^Plesk(?:L|W)in",
-        "X-Powered-By-Plesk": "Plesk"
+        "X-Powered-By-Plesk": "^Plesk"
       },
       "icon": "Plesk.png",
       "script": "common\\.js\\?plesk",
-      "website": "http://plesk.com"
+      "website": "https://www.plesk.com/"
     },
     "Pligg": {
       "cats": [