Fix bug, wrong variable used.

The variable should be `blendfile` not `scriptfilename`.
Rename megarenderoperator.py to mega_render_operator.py
Rename megarenderoperator2.py to mega_render_operator2.py
Fix using underscores in the filename
Fix missing property `scriptfilename`
Merge pull request #1 from ferhoyo/master

Fix bug, wrong variable used.