* src/cuirass/http.scm: New file.
* tests/http.scm: Likewise.
* Makefile.am (dist_pkgmodule_DATA, TESTS): Add them.
* configure.ac: Check for (json) module.

* src/cuirass/utils.scm (alist?): New procedure.
* tests/utils.scm ("alist?"): New test.

* src/schema.sql (Evaluations): Add 'revision' column.
* src/cuirass/database.scm (db-add-evaluation): Adapt.
All callers changed.

* tests/base.scm: Add missing 'test-begin' and 'test-end'.
* tests/database.scm: Likewise.
* tests/ui.scm: Likewise.
* tests/utils.scm: Likewise.

* src/schema.sql (Builds): Add 'evaluation' column.
* src/cuirass/database.scm (db-add-build): Adapt.
* src/cuirass/base.scm (build-packages): Likewise.

* Makefile.am (.scm.go): Replace $(cuirassmoduledir) by
$(pkgmoduledir).

* bin/cuirass.in (fetch-repository, compile, evaluate, build-packages)
(process-specs): Move to ...
src/cuirass/base.scm: ... here.

* src/schema.sql (Derivations): New table.
(Evaluations): Remove 'derivation' and 'job_name' columns.  Add 'id'
column.
* src/cuirass/database.scm (db-add-evaluation): Adapt.
(db-get-derivation, db-add-derivation): New procedures.
(evaluation-exists?, db-get-evaluation): Delete.
* bin/evaluate.in (main): Adapt.
* tests/database.scm ("sqlite-exec"): Likewise.
("db-add-derivation", "db-get-derivation"): New tests.
("db-add-evaluation", "db-get-evaluation"): Delete.

* bin/cuirass.in (show-help): Use 'poll' terminology.

* src/cuirass/database.scm (db-delete-evaluation): Delete.

* bin/cuirass.in (main): Change default interval value.

* bin/cuirass.in (%options): Add 'specifications' option.
(main): Use it instead of the non-option command line arguments.
(show-help): Adapt.
* README (Example): Adapt.

* tests/database/scm ("db-add-build-log"): Delete.

* tests/hello-singleton.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.

* src/cuirass/database.scm (with-database): Use 'db-open'.
(db-open): Fallback to 'db-init' if DB do not exist.

* src/cuirass/database.scm (db-open): Add DB optional argument.

This avoids code duplication.

Adapt src/cuirass/database.scm and its tests.

Export it.  Add a test.