set processor in NeuGFXWidget Constructor

[yiyin]

In order to access current ffboProcessor using the name of the processor before workspace is fully resolved, this._processor in NeuGFXWidget should be set directly by using the options.processor passed in.

The use case is to specify a custom URL from the processor settings for the NeuGFX iframe. Here is a hack in 14b5850. Might have better ways to go about it.