DB: remove shared stuff, add singleton

Add Config class

source/db/pgsql.d

@@ -5,8 +5,10 @@ import db.db;
 import ddbc.core;
 import ddbc.common;
 
+import slf4d;
+
 class PostgresDB : DB {
-  shared this(Args...)(auto ref Args args) {
+  this(Args...)(auto ref Args args) {
     super(args);
   }
 
@@ -22,6 +24,8 @@ class PostgresDB : DB {
       params = PGSQLDriver.setUserAndPassword(username, password);
     }
 
+    debugF!"DB URL: %s"(url);
+
     return new ConnectionPoolDataSourceImpl(driver, url, params);
   }
 }