Fix for issue #1746: corrected parameter hash generation.

**Issue**: #1746

**Description**: "When creating/updating an assignment, any required files you set are not persisted when you hit Submit. The Success message is displayed. however."

**Fix**: The new `input` tag that is generated for a required file is created dynamically with javascript. In this js, the input tag's name attribute is set to include `new_<TIMESTAMP>`. the `new_` breaks the functionality. Removing the `new_` from the input tag's attributes does not seem to break anything visually or code-wise.

**Testing**: I ran variations of adding and removing required files.