Add a web interface.

* Makefile.am (dist_sql_DATA): Add static files.
* src/cuirass/database.scm (assqx-ref): Export it.
(db-get-builds): Add 'evaluation' filter and filters for pagination.
(db-get-evaluations-build-summary, db-get-evaluations-id-min,
db-get-evaluations-id-max, db-get-builds-min, db-get-builds-max): New exported
procedures.
* src/cuirass/http.scm (%static-directory): New parameter.
(%page-size, %file-mime-types, %file-white-list): New variables.
(handle-build-request, handle-builds-request): Move the WITH-CRITICAL-SECTION
call out.
(url-handler): Add RESPOND-HTML, RESPOND-STATIC-FILE and RESPOND-NOT-FOUND
procedures.  Call WITH-CRITICAL-SECTION sooner for the '/build',
'/api/latestbuilds' and '/api/queue' routes.  Add '/', '/jobset/<name>',
'/eval/<id>', '/static/<path>' routes.  Use RESPOND-NOT-FOUND when the route
isn't found.
* src/cuirass/templates.scm: New file.
(html-page, specifications-table, evaluation-info-table,
build-eval-table): New exported procedures.
(pagination): New procedure.

Signed-off-by: Clément Lassieur <clement@lassieur.org>