Samigo should generate its temp directory automatically from system properties

Java already has a platform independent way to find
the system temp directory. Lets use it to do the "right" thing by
default.

http://java.sun.com/j2se/1.5.0/docs/api/java/lang/
System.html#getProperties()

java.io.tempdir Default temp file path

Find the system temp directory, then generate your working directory
beneath it based on something unique (i.e. server_id+GUID) so that
multiple instances of Sakai that run on the same OS do not have a
chance of stepping on each others' temp files.

You can always have a property available to overwrite this value with
something should the SA want to specify the place where samigo does
its temporary stuff. However I think we can get big points in the
area of User Delight for not requiring folks to worry about things
like this out of the box.

Bonus points for cleaning up the files when you are done with them.