make reverseContentLayout externally modifiable

[toya108]

Why

The reverseContentLayout is currently determined by the TOCropToolBar's semanticContentAttributes and is used when determining whether the view should be reversed left or right.

TOCropViewController/Objective-C/TOCropViewController/Views/TOCropToolbar.m

Line 64 in a942414

self.reverseContentLayout = ([UIView userInterfaceLayoutDirectionForSemanticContentAttribute:self.semanticContentAttribute] == UIUserInterfaceLayoutDirectionRightToLeft);

However, this is determined at setup time and cannot be changed later.
This makes it difficult to determine the layout direction externally.

How

Expose reverseContentLayout and allow it to be changed externally.
In addition, call setNeedsLayout in the setter to change the layout according to the changed value.

ScreenShot

CropViewControllerExample

reverseContentLayout is false	reverseContentLayout is true

TOCropViewControllerExample

reverseContentLayout is false	reverseContentLayout is true

[TimOliver]

This PR is fantastic! Thanks so much @toya108!