[models] Clear raw data in manifest after it has been read

Minor optimization to save some RAM, especially for JSON manifests.

legendary/models/json_manifest.py

@@ -53,6 +53,10 @@ class JSONManifest(Manifest):
         if _tmp.keys():
             print(f'Did not read JSON keys: {_tmp.keys()}!')
 
+        # clear raw data after manifest has been loaded
+        _m.data = b''
+        _m.json_data = None
+
         return _m
 
     @classmethod

legendary/models/manifest.py

@@ -80,6 +80,11 @@ class Manifest:
             logger.warning(f'Did not read {len(unhandled_data)} remaining bytes in manifest! '
                            f'This may not be a problem.')
 
+        # Throw this away since the raw data is no longer needed
+        _tmp.close()
+        del _tmp
+        _m.data = b''
+
         return _m
 
     @classmethod