minor improvements

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

de.srsoftware.cal.api/src/main/java/de/srsoftware/cal/api/Appointment.java

@@ -30,21 +30,18 @@ public interface Appointment {
 	 */
 	String description();
 
-
 	/**
 	 * The date and time when the appointment is scheduled to end
 	 * @return an optionals LocalDateTime
 	 */
 	Optional<LocalDateTime> end();
 
-
 	/**
 	 * represent this event as ical entry
 	 * @return the ical string
 	 */
 	String ical();
 
-
 	/**
 	 * ID of the appointment – unique within this system
 	 * @return the appointment`s id
@@ -75,14 +72,12 @@ public interface Appointment {
 	 */
 	LocalDateTime start();
 
-
 	/**
 	 * tags i.e. keywords may be used to filter appointments
 	 * @return the set of tags associated with the current appointment
 	 */
 	Set<String> tags();
 
-
 	/**
 	 * the title of the appointment
 	 * @return the title