Improve documentation of new methods in PersonalTimesheetsPeriodicityEnum

Also documented method to generate a string representing a personal timesheet in
MonthlyTimesheetDTO.

FEA: ItEr77S07PersonalTimesheetsPeriodictyConfiguration

libreplan-business/src/main/java/org/libreplan/business/common/entities/PersonalTimesheetsPeriodicityEnum.java

@@ -162,17 +162,40 @@ public enum PersonalTimesheetsPeriodicityEnum {
         return name;
     }
 
+    /**
+     * Returns the start date of the personal timesheet which includes the
+     * specified <code>date</code>.
+     */
     public abstract LocalDate getStart(LocalDate date);
 
+    /**
+     * Returns the end date of the personal timesheet which includes the
+     * specified <code>date</code>.
+     */
     public abstract LocalDate getEnd(LocalDate date);
 
+    /**
+     * Returns the number of personal timesheets between the specified dates.
+     */
     public abstract int getItemsBetween(LocalDate start, LocalDate end);
 
+    /**
+     * Returns the date of the personal timesheet in the position specified by
+     * <code>item</code> taking into account the <code>fromDate</code>.
+     */
     public abstract LocalDate getDateForItemFromDate(int item,
             LocalDate fromDate);
 
+    /**
+     * Returns the date of the previous personal timesheet to the one which
+     * includes the specified <code>date</code>.
+     */
     public abstract LocalDate previous(LocalDate date);
 
+    /**
+     * Returns the date of the next personal timesheet to the one which includes
+     * the specified <code>date</code>.
+     */
     public abstract LocalDate next(LocalDate date);
 
 }

libreplan-webapp/src/main/java/org/libreplan/web/users/dashboard/MonthlyTimesheetDTO.java

@@ -95,6 +95,10 @@ public class MonthlyTimesheetDTO {
         return toString(periodicity, date);
     }
 
+    /**
+     * Returns a string representing the personal timehseet in a given
+     * <code>date</code> depending on the <code>periodicity</code>.
+     */
     public static String toString(PersonalTimesheetsPeriodicityEnum periodicity, LocalDate date) {
         switch (periodicity) {
             case WEEKLY: