Initial commit of updated signin page with dependency injection

NOT WORKING
First pass at killing off everything m.guardian.co.uk
Merge branch 'dotcom' of github.com:guardian/frontend into theguardian-clean
Changes to OMnituire tracking

Track the URL we are on - prop 61
Correct 'cookieDomainPeriods' for www.theguardian.com'
Add theguardian.com to 'linkInternalFilters'
Merge branch 'master' of github.com:guardian/frontend into theguardian-clean
Convert tablet mqs
Media query mixin accepts other directives than widths
Abstract all media queries and convert widths into pixel values
Get rid of old breakpoints in favour of new ones
fix invalid mq rule
Add IE specific stylesheet
IE8 loads its own CSS
Merge branch 'abstract-mq' of https://github.com/guardian/frontend
Merge branch 'master' of github.com:guardian/frontend into abstract-mq
Only output SVG icons for modern browsers
Add HTML5 Shim for IE8
IE8 Sees png icons
Only output SVG rules for modern browsers
Use SVG mixin for generated sprite icons
Add injection to dev build and tweak signin