Remove invalid releases automatically (#466)

Automatically remove empty releases or releases which are released in the future, regardless of the product.

Also refactored a bit releasedata.py to use better names and clarify types.

releases/liquibase.json

@@ -1,105 +1,5 @@
 {
-  "releases": {
-    "4.9": {
-      "name": "4.9"
-    },
-    "4.8": {
-      "name": "4.8"
-    },
-    "4.7": {
-      "name": "4.7"
-    },
-    "4.6": {
-      "name": "4.6"
-    },
-    "4.5": {
-      "name": "4.5"
-    },
-    "4.4": {
-      "name": "4.4"
-    },
-    "4.32": {
-      "name": "4.32"
-    },
-    "4.31": {
-      "name": "4.31"
-    },
-    "4.30": {
-      "name": "4.30"
-    },
-    "4.3": {
-      "name": "4.3"
-    },
-    "4.29": {
-      "name": "4.29"
-    },
-    "4.28": {
-      "name": "4.28"
-    },
-    "4.27": {
-      "name": "4.27"
-    },
-    "4.26": {
-      "name": "4.26"
-    },
-    "4.25": {
-      "name": "4.25"
-    },
-    "4.24": {
-      "name": "4.24"
-    },
-    "4.23": {
-      "name": "4.23"
-    },
-    "4.22": {
-      "name": "4.22"
-    },
-    "4.21": {
-      "name": "4.21"
-    },
-    "4.20": {
-      "name": "4.20"
-    },
-    "4.2": {
-      "name": "4.2"
-    },
-    "4.19": {
-      "name": "4.19"
-    },
-    "4.18": {
-      "name": "4.18"
-    },
-    "4.17": {
-      "name": "4.17"
-    },
-    "4.16": {
-      "name": "4.16"
-    },
-    "4.15": {
-      "name": "4.15"
-    },
-    "4.14": {
-      "name": "4.14"
-    },
-    "4.13": {
-      "name": "4.13"
-    },
-    "4.12": {
-      "name": "4.12"
-    },
-    "4.11": {
-      "name": "4.11"
-    },
-    "4.10": {
-      "name": "4.10"
-    },
-    "4.1": {
-      "name": "4.1"
-    },
-    "4.0": {
-      "name": "4.0"
-    }
-  },
+  "releases": {},
   "versions": {
     "4.32.0": {
       "name": "4.32.0",