Display maven home in version info

Display maven.home information when user run "mvn -version".

Similar motivation as MNG-4944. User may have same version of maven for different project such as company/open source. Same as java.home, user may need go into maven.home to do some verification.

The patch moved java.home one line up to group together with maven.home.

With patch "mvn -version" will show:
Apache Maven 3.0.1 (r1038046; 2010-11-23 10:58:32+0000)
Maven home: /software/maven/3.0.1
Java home: /usr/lib/jvm/java-6-openjdk/jre
Java version: 1.6.0_20, vendor: Sun Microsystems Inc.
Default locale: en_IE, platform encoding: UTF-8
OS name: "linux", version: "2.6.32-25-generic", arch: "i386", family: "unix"

Without patch "mvn -version" will show:
Apache Maven 3.0.1 (r1038046; 2010-11-23 10:58:32+0000)
Java version: 1.6.0_20, vendor: Sun Microsystems Inc.
Java home: /usr/lib/jvm/java-6-openjdk/jre
Default locale: en_IE, platform encoding: UTF-8
OS name: "linux", version: "2.6.32-25-generic", arch: "i386", family: "unix"