Add Gibraltar logo to the project.

Image file came from Gibraltar as-is: I've not tweaked it at all.
Add Gibraltar logo to Sponsors page.
Add Gibraltar logo to side bar.
Update with transparentised image.

Replace the logo provided by Kendall with the tweaked one from
@adrianbanks.
Merge branch 'gibraltar-logo' of git://github.com/alastairs/DDDEastAnglia into alastairs-gibraltar-logo

Add Gibraltar logo

Conflicts:
	DDDEastAnglia/Views/Home/Sponsors.cshtml