add Sign Out settings menu
implement sign out logic
use Service to get Account info frequently
refactor
refactor SettingsPreferenceFragment
change methods and fields name more readable
improve code style according to convention
add table AccountInfo in database account.db
save account info to database
delete account info in database
always goes to AccountsActivity when no account logged in
refactor
remove fake strings
use handler to update ui

remove AccountInfoService
load account info by a child thread
fix build error
delete token only when sign out
remove unused configuration files
update gitignore to support Intellij IDEA
stop camera upload service by account
format