remove v1 backend support and version checks in the frontend

doc/Installation.md

@@ -177,11 +177,7 @@ CREATE TABLE prefix_paste (
     dataid CHAR(16) NOT NULL,
     data MEDIUMBLOB,
     expiredate INT,
-    opendiscussion INT,
-    burnafterreading INT,
     meta TEXT,
-    attachment MEDIUMBLOB,
-    attachmentname BLOB,
     PRIMARY KEY (dataid)
 );