Add mock for database loader api

src/main/java/nl/tudelft/queue/DevDatabaseLoader.java

src/test/java/nl/tudelft/queue/application/SmokeTest.java

src/test/java/test/dev/DevLcDbLoader.java

src/test/resources/application-h2-file.properties

src/test/resources/application-h2.properties

src/test/resources/application-migration.properties

src/test/resources/application-mysql.properties

src/test/resources/application-postgresql.properties