Uploading and Downloading Remixes: Client Side

Working on client side remix uploads. RemixScriptFileUtilities now reads
and writes to an arbitrary InputStream and OutputStream instead of
necessarily a file (this required making a method in IoUtilities
public). Added fields to RemixPacket and added a method to add a
RemixScript as an attachment. Modified RemixScript and
RemixScriptFactory so that scripts now contain the start and end node
UUID and the number of times the start and end nodes were executed (this
can potentially replace the rest of the script in the future). Added a
controller for downloading a RemixScript. Fixed a bug in
JsonMultipartPacket where strings were being compared with == instead of
.equals().

The client side of uploading remixes is complete barring any bugs I
find. Remixes are uploaded in AssignRolesComposite. This is where the
remix count for the remixed world was already being incremented. Rather
than saving a list of remixed world ids as a property on the project, I
save a list of remix ids (the primary key returned by the database).
I changed ShareWorldOperation so that instead of uploading the remix for
the first time, it uses the remix id list for the project to retrieve
a RemixPacket for each remix it performed. I then assigned the remixer
world id in each RemixPacket to the the community project id of the
world that is being uploaded (and thus has just received its id).