Implemented dynamic schema

Started by doing a SchemaEngine but at the end I just put everything
inside the FileEngine.

Now you can use 'schema init path/to/schema' to initialize the struct
folders and first data file, Also save a copy of the schema in a file in
the ZipponDB folder.

example.zipponschema

@@ -0,0 +1,7 @@
+User (
+  name: str,
+  age: int,
+  email: str,
+  scores: []int,
+  friends: []bool,
+)