added interface for workday and absence + multiday absences closes #38, #39

DB/initdb/01_schema.sql

@@ -91,7 +91,8 @@ CREATE TABLE "abwesenheit" (
     "counter_id" bigserial PRIMARY KEY,
     "card_uid" varchar(255),
     "abwesenheit_typ" int2,
-    "datum" timestamptz(6) DEFAULT NOW()::DATE
+    "datum_from" timestamptz DEFAULT NOW()::DATE,
+    "datum_to" timestamptz
     );
 
 DROP TABLE IF EXISTS "s_abwesenheit_typen";