harmonize Manifest properties in maven vs. ant build and fix dead project url

1. The Maven build is missing the build-timestamp, so it is not printed on startup
2. The ant build has Implementation-URL http://middleware.internet2.edu/dir/groups/grouper which is a dead link

Maven:

 Manifest-Version: 1.0

Archiver-Version: Plexus Archiver

Built-By: mchyzer

Created-By: Apache Maven 3.3.3

Build-Jdk: 1.8.0_181

Main-Class: edu.internet2.middleware.grouper.app.gsh.GrouperShell

Name: edu/internet2/middleware/grouper/

Implementation-Title: grouper

Implementation-Version: 2.4.0

Implementation-Vendor: grouper.internet2.edu

Ant (installer distro)

Manifest-Version: 1.0

Ant-Version: Apache Ant 1.9.6

Built-By: cer28

Created-By: 1.8.0_181-b25 (Oracle Corporation)

Implementation-Vendor: Internet2

Implementation-Title: grouper

Implementation-Version: 2.4.0

Implementation-URL: http://middleware.internet2.edu/dir/groups/grouper

 /

Build-Timestamp: 2018/11/08 08:20:51

The correct URL is https://www.internet2.edu/products-services/trust-identity/grouper/ (the parent pom currently defines url as http://grouper.internet2.edu which ends up there after about 6 redirects). This should be corrected in the Ant build and added to the grouper pom (and probably all the poms). They should all use the url defined in the parent pom to avoid redundant definitions.

The Maven build has no Build-TImestamp, so the startup prints "Grouper starting up: version: 2.4.0, build date: null, env: ...". This can be added, with the format matching the Ant build.

The Main-Class pointing to gsh probably isn't useful–it's not a fat jar so java -jar would miss all the dependencies.

I don't know what the manifestSection edu/internet2/middleware/grouper/ adds, since we're not sealing the package. I think just move the title, version, and vendor to the top level.