Image upload improvements (#368)

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@RocketChat/ReactNative

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- [x] Crop image
- [x] Type image description (like web)
- [x] Show upload progress
- [x] "Try again" in case of error
- [x] Cancel upload while in progress
- [x] [Android] Zoom on photos

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![image](https://user-images.githubusercontent.com/804994/42526934-a12da304-844d-11e8-8668-f3d69369726a.png)
![image](https://user-images.githubusercontent.com/804994/42527829-297945fe-8450-11e8-9f0e-9e668dd33043.png)