Add the beginnings of a feature for the site dashboard.

Handles pre-transition sites only. Not much use.
Strip out leading whitespace
Create highlight styles

* Create big number and big message styles for use with highlight
* Create highlight styles for dashboards
Add Site#transition_status
Site transition status and dates
Site dashboard configuration pane
Integrate CSS components from style guide

* Big numbers
* Margins
* Semantic shim for Bootstrap
Move things out into partials

* It was getting a little bit big in sites/show.html.erb
* Add the muted-text for mapping count
Remove Mappings/Analytics links from orgs#show

(in favour of a single link to the site dashboard)
Site#transition_status should be a symbol
Show 'overdue' status when status and launch date don't agree

* Avoids mixed messages
Cope with missing launch dates
Remove <br> from site dashboard transition date
Move data-original-title attr to title
Re-jig "days from launch" highlight pane

* Lose span stylings
* .date becomes .days-from-launch
* Remove prototype gap in favour of style guide
View/Edit mappings - style/behaviour

* People from other orgs only see a link to view mappings
* Remove redundant .list-group-item-heading style
* Swap arbitrary 18px for $default-vertical-margin
Revert to non-semantic code to keep Bootstrap happy

* ul.list-group > li.list-group-item reluctantly becomes
  div.list-group > a.list-group-item
Factor out !important colour statement

* Use specificity to override bootstraps black header colour
* Include visited link colour
* Use link colour constant
Indentation problem in _mappings.html.erb
Hard-coded hostname value replacement