Add provider templating for boot-time inheritance

[adalinesimonian]

Allows provider templates to be created, which define properties which can then
be inherited by multiple providers.

Template:

module.exports = function(config, templateConfig) {
  return {
    id: 'ActiveDirectory',
    protocol: 'ActiveDirectory',
    mapping: {
      id:          'objectGUID',
      email:       'userPrincipalName',
      name:        'name',
      givenName:   'givenName',
      familyName:  'sn',
      phoneNumber: function (info) {
        return info.telephoneNumber ||
               info.mobile ||
               info.homePhone ||
               info.otherHomePhone ||
               info.otherTelephone ||
               info.ipPhone ||
               info.otherIpPhone;
      }
    }
  };
};

Inheriting provider:

module.exports = function(config) {
  return {
    id: 'mycorpad',
    name: 'Umbrella Corp',
    templates: [ 'ActiveDirectory' ]
  };
};