static_digital_output: Add static_digital_output section to extras/

Move the code for the static_digital_output config section from
chipmisc.py to a new file in the extras/ directory.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/static_digital_output.py

@@ -0,0 +1,17 @@
+# Set the state of a list of digital output pins
+#
+# Copyright (C) 2017-2018  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+class PrinterStaticDigitalOut:
+    def __init__(self, config):
+        printer = config.get_printer()
+        ppins = printer.lookup_object('pins')
+        pin_list = [pin.strip() for pin in config.get('pins').split(',')]
+        for pin_desc in pin_list:
+            mcu_pin = ppins.setup_pin('digital_out', pin_desc)
+            mcu_pin.setup_start_value(1, 1, True)
+
+def load_config_prefix(config):
+    return PrinterStaticDigitalOut(config)