[grub] add Grub 2.0 support

* Also moves secondary Grub boot record as a resource
* Also fix a typo in README.txt and update signtool path
* Closes #340

res/grub/readme.txt

@@ -0,0 +1,10 @@
+grldr.mbr was compiled on Linux Debian 7.7.0 x64, using gcc-multilib 4.7.2,
+from https://github.com/chenall/grub4dos/commit/8549aae.
+
+Note that, for convenience reasons, the first 512 bytes from this grldr.mbr are
+*not* the ones that Rufus processes when writing the actual MBR (first 512 bytes).
+Instead, the byte array from src/ms-sys/inc/mbr_grub.h (whose content is identical)
+is what Rufus uses. If you have modified this file, and the MBR section is
+altered, be mindful that you also need to update the array in mbr_grub.h.
+
+For details, see src/format.c.

res/grub2/readme.txt

@@ -0,0 +1,16 @@
+boot.img and core.img were compiled from git://git.savannah.gnu.org/grub.git,
+commit 72ec399ad8d6348b6c74ea63d80c79784c8b84ae, on a Debian 7.7.0 x64 system.
+This was done following the guide from:
+http://pete.akeo.ie/2014/05/compiling-and-installing-grub2-for.html.
+
+boot.img has been modified to nop the jump @ 0x66 as per grub2's setup.c comments:
+
+/* If DEST_DRIVE is a hard disk, enable the workaround, which is
+   for buggy BIOSes which don't pass boot drive correctly. Instead,
+   they pass 0x00 or 0x01 even when booted from 0x80.  */
+   
+Note that, for convenience reasons, the content of boot.img is *not* the one that
+Rufus processes when writing the MBR.
+Instead, the byte array from src/ms-sys/inc/mbr_grub2.h (whose content is identical)
+is what Rufus uses. If you modify these files, be mindful that you may also need
+to update the array in mbr_grub2.h.