Read and set Classpath from Apple Plist

For Oracle Plist, use the default behaviour as it was

Thanks to Philipp Holzschneider for this contribution!
also add $USER_HOME to the list of expandable variables
for Oracle: add $APP_ROOT to the list of expandable variables
fixed reading ClassPath in either Array or String style

Either:

<key>Java</key>
<dict>
  <key>ClassPath</key>
  <string>$JAVAROOT/jarFile.jar</string>
</dict>

or:

<key>Java</key>
<dict>
  <key>ClassPath</key>
  <array>
    <string>$JAVAROOT/jarFile.jar </string>
     <string>$JAVAROOT/</string>
  </array>
</dict>

Oracle Plist with Oracle AppBundler doesn't support setting the ClassPath. It will only copy all ClassPath-Resources into the App-Bundle.
Merge pull request #5 from tofi86/dev/classpath-contrib

Read the ClassPath from Plist property