Added Habit reset Class

Immplemented a class that erases the repetitions of a habit "clearing its history"

android/uhabits-android/src/main/res/xml/preferences.xml

@@ -127,6 +127,7 @@
 
         <Preference
             android:key="resetHabits"
+            android:summary="Reset the history of all habits"
             android:title="Reset Habits"
             app:iconSpaceReserved="false" />
 

android/uhabits-core/src/main/java/org/isoron/uhabits/core/commands/ResetHabitsCommand.java

@@ -0,0 +1,45 @@
+package org.isoron.uhabits.core.commands;
+
+import androidx.annotation.NonNull;
+
+import org.isoron.uhabits.core.models.Habit;
+import org.isoron.uhabits.core.models.HabitList;
+import org.isoron.uhabits.core.models.RepetitionList;
+
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+
+public class ResetHabitsCommand extends Command
+{
+    @NonNull
+    final HabitList habitList;
+
+    @NonNull
+    final List<Habit> selected;
+
+    public ResetHabitsCommand(@NonNull HabitList habitList, @NonNull List<Habit> selected) {
+        this.habitList = habitList;
+        this.selected = new LinkedList<>(selected);
+    }
+
+    @Override
+    public void execute()
+    {
+        for (Habit h : selected) {
+            RepetitionList repetitionList = h.getRepetitions();
+            repetitionList.removeAll();
+        }
+    }
+    public List<Habit> getSelected()
+    {
+        return Collections.unmodifiableList(selected);
+    }
+
+    @NonNull
+    @Override
+    public Object toRecord() { return null;}
+
+    @Override
+    public void undo() { throw new UnsupportedOperationException();}
+}