Replaced Solium in favor of Solhint (#1575)

* Adding solhint, working on style fixes.

* Upgraded to solhint 1.5.0.

* Removed all references to Solium

* Updated mocks to make the pass the new linter rules.

* Reformatted the .solhint.json file a bit.

* Removed Solium configuration files.

* Remove Solium dependency.

* Add comment explaing disabled time rule in TokenVesting.

* Revert to the old (ugly?) style.

* Revert SignatureBouncerMock style.

* Fix ERC165InterfacesSupported interface.

contracts/mocks/ReentrancyMock.sol

@@ -24,7 +24,7 @@ contract ReentrancyMock is ReentrancyGuard {
     function countThisRecursive(uint256 n) public nonReentrant {
         if (n > 0) {
             count();
-            // solium-disable-next-line security/no-low-level-calls
+            // solhint-disable-next-line avoid-low-level-calls
             (bool success,) = address(this).call(abi.encodeWithSignature("countThisRecursive(uint256)", n - 1));
             require(success);
         }