Add public setOption()/getOption() to plupload.Uploader class.

A way to set and get configuration options in a more controllable
manner. Heavily reorganize the code for increased usability and
readability.
Address #894. Closes #901. Address #905. Closes #910. Closes #919. Closes #921.

Update moxiecode/moxie@4627caaa0e2c28a0eeb2cc66bdc65e466b5e7ede.