Benefits of the refactor:
- can support screen rotation when choosing an account
- reduce complexity in SendActivity
Also change the minSdkVersion to 7 so that
- in AccountChooserActivity, can just use the Android AccountManager
- in SendActivity, can use Account
- in SendActivity, can remove the Constants.GET_LOGIN callback
from the legacy AuthManager (AuthManagerOld)
Note using the "yyyy-MM-dd HH:mm" format so it is readable
for users. However, the colon, ":", is not a valid
FAT32 filename character. So when saving to the SD card,
the filename becomes "yyyy-MM-dd HH_mm".
Jimmy Shih