Release ELKS 0.2.0 with massive improvements

Many improvements in this commit:

- Add a script "build.sh" that makes building ELKS dead simple

- Add a script "elkscmd/image_stats.sh" to get detailed image file
  statistics such as free space and inode counts

- Fix failure to build 360K floppy images due to insufficient
  available inodes. mkfs.minix defaults to 128 inodes for a 360K
  Minix filesystem, but the minimal root filesystem "min_rfs"
  would populate the image with well over 128 inodes. A disk image
  that has no free inodes is useless anyway, so the mkfs.minix
  options were modified to make 360 inodes for all images. The
  largest image available still has over 100 inodes available when
  fully populated, so there is plenty of room for the future.

- Add a new disk image type called 'full1722'. This image is made
  to fit on a 1.722MB formatted floppy disk. Most 1.44MB floppies
  can be formatted to 1.722MB using the Linux 'fdformat' command
  and special options. The only reason this has been added is to
  increase the available disk space for capable systems.

- Improved disk image creation options. There are now four ways to
  build all of the disk images and package them up:
  make images - build all image types but don't make an archive
  make images.zip - make images into a Zip archive
  make images.tar.xz - make images into a Gzip-compressed tarball
  make images.tar.xz - make images into a XZ-compressed tarball
  (images.tar.xz compresses to about 1/7 the size of the others)

- Disk image builds will automatically link /bin/sh to either ash
  (preferred) or sash, depending on what is available.

- All disk image build types were tested in QEMU to ensure they
  boot correctly.

- Bump kernel version to 0.2.0 (yay!)

- Pre-built disk images for ELKS 0.2.0 will be made generally
  available at:  https://github.com/jbruchon/elks/releases

Special thanks to Juan Perez-Sanchez for all his recent ELKS
kernel patches!

Bump version to 0.1.5

Included patches from the "nanox" project at:

http://code.google.com/p/nanox/
which is maintained by tinybit1@gmail.com.

Changes in the patch set brought in from nanox:
* UTS_VERSION fallback date string now explicitly specified
* Cosmetic change in Makefile-rules for VSNCODE
* Readability changes in Makefile
* arch/i86/drivers/block/doshd.c bug fixes:
  * Head calculation was ANDed by 63 unnecessarily
  * A sector calculation was & 0xff, should be 0x3f
  * A cylinder calculation didn't add bits 9 and 8 back in
  * A drive head count was not added to drivep->heads

Authored-by: Unspecified <tinybit1@gmail.com>
Signed-off-by: Jody Bruchon <jody@jodybruchon.com>
Committed-by: Jody Bruchon <jody@jodybruchon.com>