refactor and cleanup [skip ci]

submodules/Postbox/Sources/Table.swift

@@ -0,0 +1,17 @@
+import Foundation
+
+open class Table {
+    public final let valueBox: ValueBox
+    public final let table: ValueBoxTable
+    
+    public init(valueBox: ValueBox, table: ValueBoxTable) {
+        self.valueBox = valueBox
+        self.table = table
+    }
+    
+    open func clearMemoryCache() {
+    }
+    
+    open func beforeCommit() {
+    }
+}