Unify build and step status codes

Also remove the obsolete status code 5 from the database.

src/sql/upgrade-46.sql

@@ -0,0 +1,5 @@
+-- Unify Builds and BuildSteps status codes.
+update BuildSteps set status = 3 where status = 4;
+
+-- Get rid of obsolete status code 5.
+update Builds set isCachedBuild = 1, buildStatus = 2 where buildStatus = 5;