Android fixes

Save/state dir worked here. I'm not sure what caused <ROM dir> to be set, but if it was due to the weird "default" value, that should be fixed now. (I really don't understand the point of setting those options to the magic "default" to begin with, but ...)

In addition, save/state dirs were forced to /data/data directory via CLI arguments from platform_android.c. That's a bit too much, since it would make it impossible to set those dirs to something else in the config (CLI arguments always override configs). Setting it to g_default was enough.

I noticed that the RetroArch config was **never** read back in Java! For some reason, this had been moved to onDestroy(), but due to broken NDK, onDestroy() is never really called. I tried exiting cleanly with JNI, finish() on Activity from UI thread and all the jazz, but to no avail, so just went for a separate JNI callback and exit() as usual ...

Rate control of 0.01 is way overkill, so reverted that. Too much actually hurts sync (and at 0.01 it starts to become audible). 0.005 is already pushing it.

Two issues I have is that a default refresh rate is not set for Shield, it seems to use the Android-reported value of 60.35 Hz or something. I don't recall if we used to have overrides for that before. RGUIs measurement reports 59.90Hz-ish at least.

Another thing is that the back button isn't doing anything after the input rewrite. Either it should quit RetroArch or bring up RGUI. There used to be an option for that I think ...