removing getLayoutMode method, use getBreakpoint
make it backwards compatiable with 'extended'
Merge branch 'master' of https://github.com/guardian/frontend into remove-get-layout

Conflicts:
	common/app/assets/javascripts/modules/experiments/tests/alpha-adverts.js
Merge branch 'master' of https://github.com/guardian/frontend into remove-get-layout
Merge branch 'master' of github.com:guardian/frontend into remove-get-layout

Conflicts:
	common/app/assets/javascripts/modules/experiments/tests/alpha-adverts.js
Merge branch 'remove-get-layout' of github.com:guardian/frontend into remove-get-layout

Conflicts:
	common/app/assets/javascripts/modules/experiments/tests/alpha-adverts.js
Merge pull request #2352 from guardian/remove-get-layout

Remove getLayoutMode, in favour of getBreakpoint