Add a status field to Evaluation table.

The Evaluation table currently has an 'in_progress' field. Distinction between
succeeded and failed evaluations are based on the presence of Builds records
for the evaluation. It it also not possible to distinguish aborted evaluations
from failed evaluations.

Rename 'in_progress' field to 'status'. The 'status' field can be equal to
'started', 'succeeded', 'failed' or 'aborted'.

* src/cuirass/database.scm (evaluation-status): New exported enumeration.
(db-set-evaluations-done, db-set-evaluation-done): Remove them.
(db-abort-pending-evaluations, db-set-evaluation-status): New exported procedures.
(db-add-evaluation, db-get-builds, db-get-evaluations,
db-get-evaluations-build-summary, db-get-evaluation-summary): Adapt to use
'status' field instead of 'in_progress' field.
* src/cuirass/templates.scm (evaluation-badges): Ditto.
* src/schema.sql (Evaluations): Rename 'in_progress' field to 'status'.
* src/sql/upgrade-10.sql: New file.
* bin/cuirass.in (main): Use "db-abort-pending-evaluations" instead of
"db-set-evaluations-done".
* src/cuirass/base.scm (evaluate): Use "db-set-evaluation-status" instead of
"db-set-evaluations-done".
(build-packages): Use "db-set-evaluation-status" instead of
"db-set-evaluation-done".
* tests/database.scm (sqlite-exec): Adapt accordingly.
* tests/http.scm (evaluations-query-result): Ditto.