Fix: Now correctly allows to override ElementFinder and ElementArrayFinder methods

[Xotabu4]

Fix: Now correctly allows to override ElementFinder and ElementArrayFinder methods

Monkey-patching was done in ElementFinder constructor against 'this'. It means this monkey-patching is applied AFTER all methods in inherited objects declared - it will just replace them. Here is list of WebElement methods, that is monkey-patched into ElementFinder:
let WEB_ELEMENT_FUNCTIONS = [
'click', 'sendKeys', 'getTagName', 'getCssValue', 'getAttribute', 'getText', 'getRect',
'isEnabled', 'isSelected', 'submit', 'clear', 'isDisplayed', 'getId', 'takeScreenshot'
];

class Component extends ElementFinder {
  constructor(elementFinder: ElementFinder) {
    super(elementFinder.browser_, elementFinder.elementArrayFinder_);
  }

 async click() {
     console.log('OWN click!')
     await super.click()
 }
}

new Component($('button')).click()

Before this PR code above would not be working - since monkey-patching is overrides methods declared in child classes:

Xotabu4/protractor-element-extend#20

[CrispusDH]

if fnName can be only string you could add this type

[CrispusDH]

do you need here () as you did for ElementFinder ((ElementFinder.prototype[fnName]))?

[CrispusDH]

@cnishina could you take a look at it useful PR? :)