Merge branch 'v2-prototype' into refactor/order-utils/for-v2

* v2-prototype: (45 commits)
  Check length before accessing indices, add awaitTransactionSuccess where needed, and rename function
  Add back before/after snapshots for each test
  Rename Signer to Wallet, rename GAS_ESTIMATE to GAS_LIMIT
  Make preSigned and allowedValidators mappings public
  Change names of signature types
  Fix formatting and tests
  Make AssetProxyId last byte of assetData
  Add signer to txHash, allow approveValidator to be used with executeTransaction
  Update Whitelist
  Fix Exchange interface
  Increase block gas limit
  Use last byte of signature as signature type
  Remove TxOrigin signature type, modify whitelist to use Validator signature type
  Update Whitelist contract with comments, also require maker to be whitelisted
  Fix build
  Add example whitelist contract and minimum tests
  Add sample whitelist contract
  Add TxOrigin signature type and rearrange order of types
  Add approveValidator function
  Add Validator signature type
  ...

# Conflicts:
#	packages/contracts/src/contracts/current/protocol/Exchange/MixinSignatureValidator.sol
#	packages/contracts/src/utils/types.ts
#	packages/contracts/test/exchange/transactions.ts
#	packages/order-utils/src/asset_proxy_utils.ts

packages/contracts/test/libraries/lib_bytes.ts

@@ -21,6 +21,7 @@ describe('LibBytes', () => {
     let owner: string;
     let libBytes: TestLibBytesContract;
     const byteArrayShorterThan32Bytes = '0x012345';
+    const byteArrayShorterThan20Bytes = byteArrayShorterThan32Bytes;
     const byteArrayLongerThan32Bytes =
         '0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef';
     const byteArrayLongerThan32BytesFirstBytesSwapped =
@@ -59,6 +60,36 @@ describe('LibBytes', () => {
         await blockchainLifecycle.revertAsync();
     });
 
+    describe('popByte', () => {
+        it('should revert if length is 0', async () => {
+            return expect(libBytes.publicPopByte.callAsync(constants.NULL_BYTES)).to.be.rejectedWith(constants.REVERT);
+        });
+
+        it('should pop the last byte from the input and return it', async () => {
+            const [newBytes, poppedByte] = await libBytes.publicPopByte.callAsync(byteArrayLongerThan32Bytes);
+            const expectedNewBytes = byteArrayLongerThan32Bytes.slice(0, -2);
+            const expectedPoppedByte = `0x${byteArrayLongerThan32Bytes.slice(-2)}`;
+            expect(newBytes).to.equal(expectedNewBytes);
+            expect(poppedByte).to.equal(expectedPoppedByte);
+        });
+    });
+
+    describe('popAddress', () => {
+        it('should revert if length is less than 20', async () => {
+            return expect(libBytes.publicPopAddress.callAsync(byteArrayShorterThan20Bytes)).to.be.rejectedWith(
+                constants.REVERT,
+            );
+        });
+
+        it('should pop the last 20 bytes from the input and return it', async () => {
+            const [newBytes, poppedAddress] = await libBytes.publicPopAddress.callAsync(byteArrayLongerThan32Bytes);
+            const expectedNewBytes = byteArrayLongerThan32Bytes.slice(0, -40);
+            const expectedPoppedAddress = `0x${byteArrayLongerThan32Bytes.slice(-40)}`;
+            expect(newBytes).to.equal(expectedNewBytes);
+            expect(poppedAddress).to.equal(expectedPoppedAddress);
+        });
+    });
+
     describe('areBytesEqual', () => {
         it('should return true if byte arrays are equal (both arrays < 32 bytes)', async () => {
             const areBytesEqual = await libBytes.publicAreBytesEqual.callAsync(