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.
Merge branch 'improving_manifest_ui' into front_dev
Bugfixes
Merge branch 'front_dev' into sign_jar

Conflicts:
	src/manifest.py
Entries in the manifest are outputted in the order in which they were parsed