Switch to using .vbprivk for signing everything now.

This makes it much simpler to keep track of what we're doing.

vbutil_key can now wrap both .keyb and .pem keys. It figures out which is
which by trying both and just using the one that works.

vbutil_keyblock and vbutil_kernel now use .vbprivk files for signing.

replace debug() with VBDEBUG(()) in host-side sources, too.

rename PrivateKeyRead to PrivateKeyReadPem

Add real PrivateKeyRead and PrivateKeyWrite for .vbprivk files.

Review URL: http://codereview.chromium.org/2871033
diff --git a/utility/vbutil_kernel.c b/utility/vbutil_kernel.c
index 8b67051..349cc8e 100644
--- a/utility/vbutil_kernel.c
+++ b/utility/vbutil_kernel.c
@@ -460,7 +460,7 @@
     return 1;
   }
 
-  signing_key = PrivateKeyReadPem(signprivate, key_block->data_key.algorithm);
+  signing_key = PrivateKeyRead(signprivate);
   if (!signing_key) {
     error("Error reading signing key.\n");
     return 1;