Add GSN to BasicAdapter, fix calculating number of registered darknodes after a Registry upgrade

[0x31]

Note - Solidity's VSCode extension now comes with a source code formatter, so there's a lot of style-only changes. See below for the specific changes.

DarknodeRegistry update

Problem Description

The DarknodeRegistry contract currently keeps track of the number of darknodes registered in the previous, current and next epoch. However, this is independent of its Store contract which holds the registration state of each darknode. If a new Registry is used against an existing Store, these numbers are out of sync.

Solution

When the DarknodeRegistry is linked to a Store, is syncs its darknode counts.

The main change to DarknodeRegistry can be found here:

https://github.com/renproject/darknode-sol/pull/86/files#diff-b69098100468efec280620252f903886R716-R742

darknode-sol/contracts/DarknodeRegistry/DarknodeRegistry.sol

Lines 716 to 742 in 1679642

	function getDarknodeCountFromEpochs(
	bool _includePreviousEpoch,
	bool _includeCurrentEpoch,
	bool _includeNextEpoch
	) private view returns (uint256) {
	// Begin with the first node in the list
	uint256 n = 0;
	address next = store.begin();
	// Iterate until all registered Darknodes have been collected
	while (true) {
	if (next == address(0)) {
	break;
	}
	if (
	(_includePreviousEpoch && isRegisteredInPreviousEpoch(next)) ||
	(_includeCurrentEpoch && isRegistered(next)) ||
	(_includeNextEpoch &&
	((isRegistered(next) && !isPendingDeregistration(next)) ||
	isPendingRegistration(next)))
	) {
	n += 1;
	}
	next = store.next(next);
	}
	return n;
	}

darknode-sol/contracts/DarknodeRegistry/DarknodeRegistry.sol

Lines 351 to 363 in 1679642

	function claimStoreOwnership() external {
	store.claimOwnership();
	// Sync state with new store.
	// Note: numDarknodesPreviousEpoch is set to 0 for a newly deployed DNR.
	numDarknodesPreviousEpoch = getDarknodeCountFromEpochs(
	true,
	false,
	false
	);
	numDarknodes = getDarknodeCountFromEpochs(false, true, false);
	numDarknodesNextEpoch = getDarknodeCountFromEpochs(false, false, true);
	}

Add GSN to Basic Adapter

The BasicAdapter contract is an example adapter, and this PR adds GSN support to it. This involves inheriting from GSNRecipient and implementing acceptRelayedCall. Currently, it accepts all relayed calls.

[loongy]

If it is left commented out, it either needs a comment explaining why it has been left here, or it should be removed.

[loongy]

@noiach coveralls reports that tests are missing for transferOwnership in the ProtocolLogic contract. Please add some tests for that, and then we can go ahead and merge.

[0x31]

I think that's the coverage for master.

See https://coveralls.io/github/renproject/darknode-sol?branch=feat/adapter-with-gsn

[0x31]

Coverage dropped (-0.08%) because of some GSN functions in an example contract that aren't tested.

[loongy]

Ok, thanks!