[main] Add input thread logic and logging

To the main application, add an input thread that "simply" reads
sys.stdin events and transmits them via core.input.

Additionally, set up some initial logging (yeah, for threading, this is
needed immediately)

core/input.py

@@ -1,4 +1,6 @@
 import uuid
+import logging
+
 import util.cli
 
 LEFT_MOUSE = 1
@@ -7,6 +9,14 @@ RIGHT_MOUSE = 3
 WHEEL_UP = 4
 WHEEL_DOWN = 5
 
+def button_name(button):
+    if button == LEFT_MOUSE: return 'left-mouse'
+    if button == RIGHT_MOUSE: return 'right-mouse'
+    if button == MIDDLE_MOUSE: return 'middle-mouse'
+    if button == WHEEL_UP: return 'wheel-up'
+    if button == WHEEL_DOWN: return 'wheel-down'
+    return 'n/a'
+
 callbacks = {}
 
 class Object(object):
@@ -18,6 +28,7 @@ class Object(object):
         return self._id
 
 def register(obj, button=None, cmd=None):
+    logging.debug('registering callback {} {}'.format(obj.id(), button))
     callbacks.setdefault(obj.id(), {}).setdefault(button, []).append(cmd)
 
 def trigger(event):