Auto upload photos taken by the Camera

I added the auto upload photos function but not finished yet. There are still a lot of design stuff needs to be discussed, and [from here](https://github.com/haiwen/seadroid/issues/7) you can see what we have discussed before.
* if user choose a photo folder to auto upload, should the app create a new folder exact the same name with the local one on cloud. What if user choose multi-folders, should the app create the same number of folders on cloud? I learnt that both Baidu Pan and 360 Cloud auto upload users photos to one particular folder rather than creating many.
* Is it necessary for users to start or disable auto upload function manually based on their needs. 
* I think the app is supposed to auto upload all photo folders from SD card to the cloud, not just several.
* I created a new branch called `lguo`, and please check out the project, run the app and give me some advice. note that, the auto upload function is not finished yet, I didn`t implement the uploading function.
* and more....