Better usage messages when number of command-line arguments is wrong
Digest algorithms can be specified for "manifest -c".

The default behavior is not affected. When "-d" or "--digest" option
is given, the list of digest algorithms as wanted in the JAR should
follow. For example, "manifest -c -d MD5,SHA-512" will create
digests with md5 and sha512 algorithms.
Signature of digest_chunks restored to original, SHA1 used for Java digest name instead of SHA-1
Merge pull request #5 from KonstantinShemyak/select_digest_algorithms

Digest algorithms can be specified for "manifest -c".
Merge pull request #6 from KonstantinShemyak/improving_manifest_ui

Better usage messages when number of command-line arguments is wrong