Defined VERSION to be edited during a build.

VERSION is defined to be a string containing the current version. This definition should be modified during a build to insert the current version, so that it can be output with the 'version' command.
Add fingerprint and ctime to new repositories.

The Chicken egg simple-sha1 is used to generate sha1sums from strings, and in the future can be used on files as well. A fingerprint for the repository is now generated by obtaining the sha1sum of the current Unix time. The current Unix time is also stored in the ctime field. The design documentation has been updated to reflect the fact that dates stored refer to the number of seconds since Januay 1, 1970.