[css] Update bootstrap
[views] NotAuthorized: use callout instead of alert css classes
[views] InternalServerError: new error page for exceptions
GCAAuth: use new InternalServerError html page
[js/model] Conference +{start, end deadline, logo, thumbnail}
[views] adminConference: new page for conference admins
[routes+controller] new {create, admin}Conference
[views] admin/conference: add max-width to the form
[views] conference:  link to admin page and del owner stuff
[views] adminConference: be sensitive to submission state
[service] Conference, on update, try to use existing topic

This will fix the bug that on save we basically duplicate the
all topics.
[views] adminConference: add simple UI for topic changes
[service] Conference: Add orphanRemoval for topics

This fixes reappearing topics that have been deleted after restart.
Merge pull request #96 from gicmo/adminConference

Admin page for conference