Remove the file UserIdentity.ts

[VictorNS69]

The idea is to remove the file UserIdentity.ts.

It has been thought that the lib should not encapsulate signing and sending, so the lib consumer should use it to create the transactions and then sign and send it as desired.

The only function that needs to be maintained is

alastria-identity-lib/src/UserIdentity.ts

Lines 96 to 103 in fa6a3d9

	private async getUserNonce(endPoint, address) {
	try {
	return await endPoint.eth.getTransactionCount(address)
	} catch (err) {
	console.log(err)
	throw err
	}
	}

The idea is to use the directory utils for common funcitons, as getUserNonce. So a new file needs to be created there with this function (and the others that are needed).

This issue will need the examples to be modified too.

[VictorNS69]

This will remove one lib in the #125 (no tx-signer)