Common account picker similar to the standard framework account picker introduced in ICS.
Documentation: http://developer.android.com/reference/com/google/android/gms/common/AccountPicker.html
Returns an intent to an Activity that prompts the user to choose from a list of accounts. The caller will then typically start the activity by calling startActivityForResult(intent, ...);.
On success the activity returns a Bundle with the account name and type specified using keys KEY_ACCOUNT_NAME and KEY_ACCOUNT_TYPE.
