Massive refactoring of all code + audio skeleton.

This should make it easier to find files and (in the future) split things
up into separate libraries.
It also changes around emulator initialization to make it a little more
difficult to do things out of order and a little more sensible as to when
real init work happens.
Also adding a skeleton audio system/driver and reworking CPU register
access to be more extensible.

src/xenia/apu/nop/sources.gypi

@@ -0,0 +1,12 @@
+# Copyright 2013 Ben Vanik. All Rights Reserved.
+{
+  'sources': [
+    'nop_apu-private.h',
+    'nop_apu.cc',
+    'nop_apu.h',
+    'nop_audio_driver.cc',
+    'nop_audio_driver.h',
+    'nop_audio_system.cc',
+    'nop_audio_system.h',
+  ],
+}