JS client: Model methods should be added to prototype

[delenius]

In the generated model classes, each instance contains the methods constructFromObject, toJson, plus getters and setters for all the fields. Currently, these methods are added as anonymous functions to each instance. Meaning, if I have 100 instances of some class, I have 100 copies of each of the methods.

These should be added to the class's prototype instead. For example, instead of (current version)

var Person = function Person(name) {
  var self = this;
  self['name'] = name;
  self['age'] = age;
  self.constructFromObject = function(data) {
      if (!data) {
        return this;
      }
      self['name'] = ApiClient.convertToType(data['name'], 'String');
      return this;
  }
  self.getName = function() {
    return self['name'];
  }
  self.setName = function(name) {
    self['name'] = name;
  }
  self.toJson = function() {
    return JSON.stringify(self);
  }
}

it should generate (new version):

var Person = function Person(name) {
  this['name'] = name;
}

Person.prototype.constructFromObject = function(data) {
  if (!data) {
    return this;
  }
  this['name'] = ApiClient.convertToType(data['name'], 'String');
  return this;
}

Person.prototype.getName = function() {
  return this['name'];
}

Person.prototype.setName = function(name) {
  this['name'] = name;
}

Person.prototype.toJson = function() {
  return JSON.stringify(this);
}

Two additional comments:

1. It would be nice to be able to omit the getters and setters entirely, as they cause a lot of bloat that is not desired in many cases.
2. The toJson prototype is the same for every model, and could be moved to a higher level prototype:

var ApiModel = function(){}
ApiModel.prototype.toJson = function() { return JSON.stringify(this); }

var Person = function Person(name) {
  ApiModel.call(this);
  this['name'] = name;
}

// all the Person prototype function follow like before, except toJson

[delenius]

I submitted a PR. Note that it does not deal with the two "additional comments" above.