Fix autologin for non-skinned apps when credentials are invalid

If there is an instance code available, we need to attempt an automatic
login before we can decide whether to dispatch to TabLayout or
InstanceSwitcherActivity

Fixes #89
Fix logging in from the Instance Switcher Activity

Logging was attempting to call App.reloadInstanceInfo without having an
instance code set (which makes sense from the instance switcher activity)

Fixes #88
Fix race condition that caused the InstanceSwitcher to hang

Because onResume can be called multiple times, occasionally the
"loading instances" would never be dismissed.  Changing to onStart fixes
this, as it only gets called once per Intent

During investigation of this, I also determined that setting
InstanceSwitcherActivity to use singleTop seems to be unnecessary
Fix some lint