Draft and lifecycles directories cleanup (#2122)

* Move Pausable into utils

* Move Strings into utils

* Move Counters into utils

* Move SignedSafeMath into math

* Remove ERC1046

* Make ERC20Snapshot.snapshot internal

* Move ERC20Snapshot into ERC20

* Add drafts deprecation notice

* Remove drafts directory

* Add changelog entry

* Apply suggestions from code review

Co-Authored-By: Francisco Giordano <frangio.1@gmail.com>

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

Author: nventuro

CHANGELOG.md

@@ -4,6 +4,11 @@
 
 ### Breaking changes
  * `ECDSA`: when receiving an invalid signature, `recover` now reverts instead of returning the zero address. ([#2114](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2114))
+ * `Pausable`: moved to the `utils` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
+ * `Strings`: moved to the `utils` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
+ * `Counters`: moved to the `utils` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
+ * `SignedSafeMath`: moved to the `math` directory. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
+ * `ERC20Snapshot`: moved to the `token/ERC20` directory. `snapshot` was changed into an `internal` function. ([#2122](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2122))
  * `Ownable`: moved to the `access` directory. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))
  * `Ownable`: removed `isOwner`. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))
  * `Secondary`: removed from the library, use `Ownable` instead. ([#2120](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2120))

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -6,4 +6,6 @@ These are math-related utilities.
 
 {{SafeMath}}
 
+{{SignedSafeMath}}
+
 {{Math}}

contracts/drafts/README.adoc

@@ -1,6 +1,6 @@
 pragma solidity ^0.6.0;
 
-import "../drafts/Counters.sol";
+import "../utils/Counters.sol";
 
 contract CountersImpl {
     using Counters for Counters.Counter;

contracts/lifecycle/README.adoc

@@ -1,13 +1,17 @@
 pragma solidity ^0.6.0;
 
-import "../drafts/ERC20Snapshot.sol";
+import "../token/ERC20/ERC20Snapshot.sol";
 
 
 contract ERC20SnapshotMock is ERC20Snapshot {
     constructor(address initialAccount, uint256 initialBalance) public {
         _mint(initialAccount, initialBalance);
     }
 
+    function snapshot() public {
+        _snapshot();
+    }
+
     function mint(address account, uint256 amount) public {
         _mint(account, amount);
     }

contracts/math/README.adoc

@@ -1,6 +1,6 @@
 pragma solidity ^0.6.0;
 
-import "../lifecycle/Pausable.sol";
+import "../utils/Pausable.sol";
 
 contract PausableMock is Pausable {
     bool public drasticMeasureTaken;