TWRP-ify AOSP code

Pull in most TWRP sources
Stub out partition management code
Make it compile -- probably will not boot
Kind of a mess but have to start somewhere
diff --git a/libcrecovery/defines.h b/libcrecovery/defines.h
new file mode 100644
index 0000000..d94ad2d
--- /dev/null
+++ b/libcrecovery/defines.h
@@ -0,0 +1,2 @@
+#undef _PATH_BSHELL
+#define _PATH_BSHELL "/sbin/sh"