Text secure attachments ui

This PR handles the UI for Image Attachments.

## In Conversation : 
Image Attachments are correctly displayed, with different views for portrait and landscape views. Also attachment previews are bigger on iPhone 6/6+

## Full Image View : 
Handling for full preview of image, zoomable, scrollable, pincheable, etc. Sharing options include saving to camera roll, copying to pasteboard, and deleting the image (to be implemented).

## Misc : 
 A UIDevice category for finding out what kind of hardware is used.

## ScreenShots
![img_7124](https://cloud.githubusercontent.com/assets/5308013/5519261/344e4924-894b-11e4-802e-b2b7680f6fa1.PNG)
![img_7125](https://cloud.githubusercontent.com/assets/5308013/5519276/da6d65e2-894b-11e4-9375-1efba9e5a007.PNG)
![img_7126](https://cloud.githubusercontent.com/assets/5308013/5519277/dc8d46bc-894b-11e4-86ce-15f4fb7525a1.PNG)
![img_7127](https://cloud.githubusercontent.com/assets/5308013/5519279/de2b85c4-894b-11e4-872e-42a7fb9250b9.PNG)