Merge branch 'hotfix/0.18.0.12'
Update changelog version number
Clarify RESPONSIVE_STYLING setting
Update translations
note commonlib update in changelog
Update ALAVETELI_VERSION
Add note about HighlightHelper#excerpt backport

Requires Hash options
Update translations
Update translations
Update translations
Update translations
Update translations
Use null values for general settings

mySociety’s internal deployment system requires these to be
set in some capacity (even if the value is null).
Merge branch 'general-null-values' into rails-3-develop
Fix translation bug in variable interpolation
Merge remote-tracking branch 'origin/release/0.19'
Merge branch 'master' into rails-3-develop

Conflicts:
	locale/cy/app.po
Allow RAILS_ENV to be set in sysvinit-thin

Install script on AWS uses development mode by default
Move method to model to make it more testable, add spec.
Use path relative to Rails root.