Changed digest that is being stamped from $parent_commit_hash, to
shaX(parent:$parent_commit_hash,tree:$tree_hash)
where shaX is the hash function used by the repository.
This change is so that the timestamp added also timestamps the
LTV data that is being added with the timestamp commit.
This LTV data now also contains CRLs for the LAST timestamp commit.
This ensures that timestamp lifetime of old timestamps gets
arbitrarily extended into the future with every new timestamp
added to the repository.
Further changes:
-Updated documentation
-updated schematics and changed from SVG to PNG
-added assertions, pre- and post-conditions
-added version number to timestamp commits as trailer
-added hashing algorithm used as trailer
-added digest being timestamped as trailer
-added the string that is hashed to get the digest as traile
-improved log messages of validate.sh
