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.

tools/tools.gypi

@@ -2,6 +2,6 @@
 {
   'includes': [
     'xenia-run/xenia-run.gypi',
-    'xenia-test/xenia-test.gypi',
+    #'xenia-test/xenia-test.gypi',
   ],
 }