Use Flyway to deploy SQL schema to non-prod

Added Gradle tasks to deploy and drop schema in alpha
using Flyway.

Use a custome dialect in GenerateSqlSchemaCommand to
convert varchar type to 'text' and timestamp to 'timestamptz'.

Corrected ClaimsEntry's revision_id column type to int8.
This column tracks parent table's primary key and should
not be bigserial.

gradle.properties

@@ -14,4 +14,4 @@ enableDependencyLocking=true
 dbServer=
 dbName=postgres
 dbUser=
-dbPassword=
+dbPassword=