Log Message:
Update to 20090513.

Changes:
- Skip blank lines in batch file
- Minor documentation change
- Update and correct (format,extension) table for YouTube
- Added -b option and created option groups for help prompt
- Fixed ambiguity of multiple video option specifiers by dissalowing it;
  changed some sys.ext calls to parser.error
- Some consistency changes and ghost-file bugfix
- Move the -t and -l options to the filesystem group
- Add format 35 (flv) as second best in quality
- Add an "epoch" keyword to the output template
- Use store_const instead of append_const as the latter requires Python 2.5