Add panels based layouts for clean_960gs

I tried to do a code review using dreditor but the review was so huge and I don’t want to put you off!

Here is my condensed review which will hopefully make it easier for you to carry out the fixes:

• There is info added by the packaging scripts in the info file. Please remove this.
• All files are missing @file directives.
• Please remove all trailing whitespace.
• Ensure code comments end with a full stop.
• Don’t use markup to clear. Use .clear-block on the container instead.
• There are missing commas off the end of some of the plugin definition arrays.
• Some plugin definitions have a comment. We should either add a comment to all plugin definitions or remove them all to be consistent. If we add a @file directive with proper description then we won’t need this comment anyway so I recommend removing them.
• Some files are missing a newline at the end of the file.
• Indentation of some plugin definitions is screwy.
• There is a comment above one of the plugin definitions that reads “implementations of hookpanelslayouts”. Please remove this.
• Do we need to define a CSS file for each layout if it’s only going to be empty?

If there are any of these items that you don’t want to fix, please add a comment explaining your reasoning.