appium#52 Add @FindBy annotations for appium's extra locator strategies

WebElement can be instantiated by these ways:
```java
@FindBy(someStrategy) //for browser or Html UI
@AndroidFindBy(someStrategy) //for Android UI of the same application. Strategies are:
//uiAutomator, accessibility, id, name, className, tagName, xpath
//@AndroidFindBys({@AndroidFindBy(someStrategy1), @AndroidFindBy(someStrategy2)}) is for chained search

@iOSFindBy(someStrategy) //for iOS UI of the same application. Strategies are:
//uiAutomator, accessibility, id, name, className, tagName, xpath
//iOSFindBys({@iOSFindBy(someStrategy1), @iOSFindBy(someStrategy2)}) is for chained search
WebElement someElement;
```

or 

```java
@FindBy(someStrategy)
@AndroidFindBy(someStrategy) 
@iOSFindBy(someStrategy)
RemoteWebElement someElement;
```

or 

```java
@AndroidFindBy(someStrategy) 
@iOSFindBy(someStrategy)
MobileElement someElement;
```

Now old browser page objects can be reusable with this decorator:
```java
PageFactory.initElements(new AppiumFieldDecorator(driver), pageObject);
```

or 

```java
PageFactory.initElements(new AppiumFieldDecorator(driver, 
	      15, //default implicit waiting timeout for all strategies
		TimeUnit.SECONDS), 
			pageObject);
```

I made some tests. If there is not enough please add your own.