Display a site's transition status

Also allow you to record the special redirect strategy for a site.

Based heavily on @jennyd's code.
Eager load hosts to reduce number of queries
Move transition status column to left of launch date
Add tooltips explaining indeterminate statuses
Rename launch date to transition date

* Launch is confusing language
* Rename launch date to transition date
* Don’t infer state of transition via date, rename “not yet launched”
to “no date set”
Move transition status to partial

* Put all redirect strategy information into a tooltip
* Remove the opacity on the glyphicon, bootstrap 3 icons match the font
colour
* Lowercase transition in “Pre-transition”
Add transition status and date to site details
Merge pull request #131 from alphagov/site_transition_state_alternative

Site transition state (alternative)