Create a history item when changing entries.

Closes #15

src/core/EntryAttributes.cpp

@@ -149,6 +149,33 @@ bool EntryAttributes::areCustomKeysDifferent(const EntryAttributes* other)
     return false;
 }
 
+EntryAttributes& EntryAttributes::operator=(const EntryAttributes& other)
+{
+    if (*this != other) {
+        Q_EMIT aboutToBeReset();
+
+        m_attributes = other.m_attributes;
+        m_protectedAttributes = other.m_protectedAttributes;
+
+        Q_EMIT reset();
+        Q_EMIT modified();
+    }
+
+    return *this;
+}
+
+bool EntryAttributes::operator==(const EntryAttributes& other) const
+{
+    return (m_attributes == other.m_attributes
+            && m_protectedAttributes == other.m_protectedAttributes);
+}
+
+bool EntryAttributes::operator!=(const EntryAttributes& other) const
+{
+    return (m_attributes != other.m_attributes
+            || m_protectedAttributes != other.m_protectedAttributes);
+}
+
 void EntryAttributes::clear()
 {
     Q_EMIT aboutToBeReset();