Remove old sql code

src/main/java/de/tobias/playpad/server/sql/ColumnName.java

src/main/java/de/tobias/playpad/server/sql/ForeignKey.java

src/main/java/de/tobias/playpad/server/sql/Id.java

src/main/java/de/tobias/playpad/server/sql/Table.java

src/main/scala/de/tobias/playpad/server/project/Pad.scala

.../tobias/playpad/server/project/loader/sql/PadLoader.scala

...scala/de/tobias/playpad/server/sql/SqlResultHandler.scala

...in/scala/de/tobias/playpad/server/sql/SqlSerializer.scala

...de/tobias/playpad/server/sql/StringSqlResultHandler.scala

...a/de/tobias/playpad/server/sql/UUIDSqlResultHandler.scala