HTTP password input field should not allow longer than 16 characters

[glynhudson]

Password is currently limited to 16 characters but it is possible for a user to enter a longer password which results in silent failure then user is unable to login since password in truncated.This could be fixed by a hard limit on the password input field.

https://community.openenergymonitor.org/t/reset-http-auth-password-on-esp8266/11159

[CircuitSetup]

Fixed this in config.js under the admin save event:

self.saveAdminFetching = ko.observable(false);
  self.saveAdminSuccess = ko.observable(false);
  self.saveAdmin = function () {
    var adminsave = {
        user: self.config.www_username(),
        pass: self.config.www_password()
    };

    if (adminsave.user.length > 16 || adminsave.pass.length > 16) {
        alert("Please enter a username and password that is 16 characters or less");
    } else {
    self.saveAdminFetching(true);
    self.saveAdminSuccess(false);
    $.post(baseEndpoint + "/saveadmin", adminsave, function (data) {
      self.saveAdminSuccess(true);
    }).fail(function () {
      alert("Failed to save Admin config");
    }).always(function () {
      self.saveAdminFetching(false);
    });
   }
  };