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Description

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Adds a button to change the orientation of the the split editing window to allow either vertical or horizontal

<img width="1552" alt="Screenshot 2019-03-19 at 20 55 31" src="https://user-images.githubusercontent.com/33291351/54641324-db326a00-4a89-11e9-9610-71746800cc78.png"> <img width="1552" alt="Screenshot 2019-03-19 at 20 55 38" src="https://user-images.githubusercontent.com/33291351/54641325-db326a00-4a89-11e9-9022-a4944e061da3.png">

Issue fixed

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#2903

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Type of changes

• :white_circle: Bug fix (Change that fixed an issue)
• :white_circle: Breaking change (Change that can cause existing functionality to change)
• :white_circle: Improvement (Change that improves the code. Maybe performance or development improvement)
• :radio_button: Feature (Change that adds new functionality)
• :white_circle: Documentation change (Change that modifies documentation. Maybe typo fixes)

Checklist:

• :radio_button: My code follows the project code style
• :white_circle: I have written test for my code and it has been tested
• :radio_button: All existing tests have been passed
• :radio_button: I have attached a screenshot/video to visualize my change if possible