Add secure property to environment in Configuration

This is populated by Play's configuration so it can switch on the
currently running application. Each sub-project can specify if it
should be run securely.

The value of this secure property is used to choose the correct URLs
for URL path values elsewhere in the config.
Add thegulocal to CORS origin property
Merge remote-tracking branch 'origin/master' into secure-configuration

Conflicts:
	common/app/common/configuration.scala
Adding colour chart and type scale
File rename
Reinstate social sign in icons
Fixed typo in font scale
Merge pull request #1905 from guardian/identity-social-signin-icons

Reinstate social sign in icons
Merge pull request #1903 from guardian/design-docs

Design documentation
Merge pull request #1822 from guardian/secure-configuration

Secure configuration
Merge branch 'master' into frontend-build

Conflicts:
	common/app/assets/AssetsPlugin.scala
	common/app/assets/images/global/sprite.png
	common/app/common/StaticAssets.scala
	common/app/conf/application.scala
	identity/conf/play.plugins