[packager] Classpath separator internally inconsistant

The handling of the classpath variable inside of the packager is inconsistent. In some cases it is whitespace, in others it is path separator.

Unify this so internally it is spaces. When an external string is stored convert the File.separatorChar into spaces.

This fixes a corner case where classpath and applicaitonClass are passed in, and classpath is File.separatorChar delimited. The mainClassJar was not identified.