Implement a storage update mechanism (for FileStorage)

The idea is pretty simple: get the current database version and for each
older version, do what needs to be done in order to get to the next
version state. This will make schema changes transparent to the user in
case they are needed.

pyrogram/client/storage/file_storage.py

@@ -67,6 +67,17 @@ class FileStorage(SQLiteStorage):
         # noinspection PyTypeChecker
         self.update_peers(peers.values())
 
+    def update(self):
+        version = self.version()
+
+        if version == 1:
+            with self.lock, self.conn:
+                self.conn.execute("DELETE FROM peers")
+
+            version += 1
+
+        self.version(version)
+
     def open(self):
         path = self.database
         file_exists = path.is_file()
@@ -97,6 +108,8 @@ class FileStorage(SQLiteStorage):
 
         if not file_exists:
             self.create()
+        else:
+            self.update()
 
         with self.conn:
             try:  # Python 3.6.0 (exactly this version) is bugged and won't successfully execute the vacuum