Create an ES6 Class from lets-encrypt-acme-client.js

[FirstTimeEZ]

Currently you can only have one daemon, which doesn't really make much sense if you have a more complicated setup
lets-encrypt-acme-client.js should be turned into an ES6 Class so there can be multiple instances of it.

/**
 * Create an `LetsEncrypt! Daemon` to Manage a `SSL Certificate`
 * 
 * @see startLetsEncryptDaemon - The actual daemon that will run periodcally after being started to create/renew certificates
 * @see checkChallengesMixin - You must check the `HTTP-01` challenges for each daemon you create
 * @remark `internal` methods could change at any time
 **/
export class LetsEncryptDaemon {
    constructor() {
        this.challengeLists = [];
        this.httpChallenges = [];
        this.checkAnswersFlag = false;
        this.localHost = false;
        this.checkedForLocalHost = false;
        this.acmeKeyChain = undefined;
        this.jsonWebKey = undefined;
        this.jsonWebKeyThumbPrint = undefined;
        this.acmeDirectory = null;
        this.acmeDirectoryURL = DIRECTORY_PRODUCTION;
        this.one = false;
        this.ariWindow = null;
        this.remaining = { days: null, hours: null, minutes: null };
    }

    async startLetsEncryptDaemon(fqdns, sslPath, certificateCallback, optGenerateAnyway = false, optStaging = false, dnsProvider = undefined) { }

    checkChallengesMixin(req, res) {  }

    async internalUpdateDirectory() {  }

    async internalCheckAnswered() {  }
    
    async internalGetAcmeKeyChain(sslPath) {   }

    async internalLetsEncryptDaemon(fqdns, sslPath, certificateCallback, optStaging, dnsProvider) {    }

    async internalFetchSuggest(sslPath, acmeDirectory) {  }

    async internalUpdateSuggestFromText(certificateText, acmeDirectory) {  }

    internalCheckForLocalHostOnce(req) {  }

    internalCheckChallenges() { }

    internalDetermineRequirement(fqdns, certFilePath, optStaging) {  }

    internalExpireDateFromCertificate(__certPath) {  }
}

closes #3