Some stuff for programmatically work with SimpleCam

I need to automatically acquire a photo from the camera without the user interaction so I've adde the following features:

- Callback ```simpleCamDidLoadedCamera:``` for check when the camera is correctly displaying the stream.
- Method ```capturePhoto``` for programmatically take a photo.
- Method ```setDisablePhotoPreview``` for avoid the preview phase and directly allow the developer to work with the acquired photo.
- Methods ```setHideCaptureButton`` and ```setHideBackButton``` for avoid user to interact with and automatic acquiring phase.

Those features will allow developer to use SimpleCam both programmatically or with user interaction.