Add option to use syn.store() without exercising multithreads
This enable synapser users to upload large file without running into Cstack problem.
Kenny pointed me to this fix.
Validated that single threaded upload worked.
tested w/ a 80MB file and saw that the progress updated sequentially in 8MB chunks when synapseclient.config.single_threaded=True and that it updated in larger chunks when synapseclient.config.single_threaded=False depending on the timing of the threads.
I have to note that the performance hit when uploading in single thread mode is huge.