Add capped interface, python interface and test for capped, expire

solidity/Capped.sol

@@ -0,0 +1,12 @@
+pragma solidity >=0.6.12;
+
+// Author:	Louis Holbrook <dev@holbrook.no> 0826EDA1702D1E87C6E2875121D2E7BB88C2A746
+// SPDX-License-Identifier:	AGPL-3.0-or-later
+// File-version: 1
+
+interface ICapped {
+	// Supply limit is changed.
+	event Cap(uint256 indexed _oldCap, uint256 _newCap);
+	// Return the supply limit.
+	function maxSupply() external returns(uint256);
+}

solidity/Writer.sol

@@ -18,5 +18,5 @@ interface IWriter {
 	function deleteWriter(address _writer) external returns (bool);
 
 	// Check whether the given address is a writer.
-	function isWriter(address _writer) external returns (bool);
+	function isWriter(address _writer) external view returns (bool);
 }