Emulate multipart upload with single-part uploads

This approach requires three times as many operations as the optimal
approach.  Implementing this correctly requires exposing the
underlying multipart operations in jclouds.  Most s3-tests pass but
two still fail:

test_multipart_upload_size_too_small
test_list_multipart_upload

References #2.

src/main/java/org/gaul/s3proxy/S3ErrorCode.java

@@ -51,6 +51,7 @@ enum S3ErrorCode {
             "Length Required"),
     NO_SUCH_BUCKET(HttpServletResponse.SC_NOT_FOUND, "Not Found"),
     NO_SUCH_KEY(HttpServletResponse.SC_NOT_FOUND, "Not Found"),
+    NO_SUCH_UPLOAD(HttpServletResponse.SC_NOT_FOUND, "Not Found"),
     REQUEST_TIME_TOO_SKEWED(HttpServletResponse.SC_FORBIDDEN, "Forbidden"),
     REQUEST_TIMEOUT(HttpServletResponse.SC_BAD_REQUEST, "Bad Request"),
     SIGNATURE_DOES_NOT_MATCH(HttpServletResponse.SC_FORBIDDEN, "Forbidden");