Another huge batch of registry v2 changes

Add patch support and resumeable sha
Implement all actual registry methods
Add a simple database generation option

util/registry/filelike.py

@@ -0,0 +1,24 @@
+class SocketReader(object):
+  def __init__(self, fp):
+    self._fp = fp
+    self.handlers = []
+
+  def add_handler(self, handler):
+    self.handlers.append(handler)
+
+  def read(self, n=-1):
+    buf = self._fp.read(n)
+    if not buf:
+      return ''
+    for handler in self.handlers:
+      handler(buf)
+    return buf
+
+  def tell(self):
+    raise IOError('Stream is not seekable.')
+
+
+def wrap_with_hash(in_fp, hash_obj):
+  wrapper = SocketReader(in_fp)
+  wrapper.add_handler(hash_obj.update)
+  return wrapper