Added libraries for unix4j to augment internal commands. #4

Unix4j found at https://code.google.com/p/unix4j/ and will soon be
cloned into my own repo for my own tinkering.
Forgot to add the unix4j llibraries to my Eclipse project classpath. #4
#22 Partially implemented the "set" command.

The "alias" command is still lacking, although I would make it do the
same as "set".

The "set" command works with single-word commands, but mullti-part
commands (like "java -version") until the Command class is able to
properly parse quotation marks.