Remove unused grid system css
Prefix layout classes with l-
Rename files
Merge branch 'master' of github.com:guardian/frontend into remove-layoutcss

Conflicts:
	common/app/assets/stylesheets/module/commercial/_travel.scss
Coding conventions
remove unused caption fragment
Deprecate box-indent class
Deprecate box-indent class
Merge pull request #4114 from guardian/remove-layoutcss

CSS layout architecture improvements