Fix #459 - properly support remote SPI with pigpio

Sorry! Dave's messing around with the pin implementations again.
Hopefully the last time. The pin_factory is now really a factory object
which can be asked to produce individual pins or pin-based interfaces
like SPI (which can be supported properly via pigpio).

gpiozero/__init__.py

@@ -6,8 +6,9 @@ from __future__ import (
 )
 
 from .pins import (
+    Factory,
     Pin,
-    LocalPin,
+    SPI,
 )
 from .pins.data import (
     PiBoardInfo,
@@ -15,47 +16,9 @@ from .pins.data import (
     PinInfo,
     pi_info,
 )
-from .exc import (
-    GPIOZeroError,
-    DeviceClosed,
-    BadEventHandler,
-    BadWaitTime,
-    BadQueueLen,
-    CompositeDeviceError,
-    CompositeDeviceBadName,
-    CompositeDeviceBadOrder,
-    CompositeDeviceBadDevice,
-    SPIError,
-    SPIBadArgs,
-    EnergenieSocketMissing,
-    EnergenieBadSocket,
-    GPIODeviceError,
-    GPIODeviceClosed,
-    GPIOPinInUse,
-    GPIOPinMissing,
-    InputDeviceError,
-    OutputDeviceError,
-    OutputDeviceBadValue,
-    PinError,
-    PinInvalidFunction,
-    PinInvalidState,
-    PinInvalidPull,
-    PinInvalidEdges,
-    PinSetInput,
-    PinFixedPull,
-    PinEdgeDetectUnsupported,
-    PinPWMError,
-    PinPWMUnsupported,
-    PinPWMFixedValue,
-    PinUnknownPi,
-    PinMultiplePins,
-    PinNoPins,
-    GPIOZeroWarning,
-    SPIWarning,
-    SPISoftwareFallback,
-    PinWarning,
-    PinNonPhysical,
-)
+# Yes, import * is naughty, but exc imports nothing else so there's no cross
+# contamination here ... and besides, have you *seen* the list lately?!
+from .exc import *
 from .devices import (
     Device,
     GPIODevice,