[App][Gui]Add Filter for PropertyFile in PropertyEditor

src/App/PropertyFile.cpp

@@ -630,7 +630,7 @@ TYPESYSTEM_SOURCE(App::PropertyFile , App::PropertyString)
 
 PropertyFile::PropertyFile()
 {
-
+    m_filter = "";
 }
 
 PropertyFile::~PropertyFile()
@@ -638,3 +638,13 @@ PropertyFile::~PropertyFile()
 
 }
 
+void PropertyFile::setFilter(const std::string f)
+{
+    m_filter = f;
+}
+
+std::string PropertyFile::getFilter(void) const
+{
+    return m_filter;
+}
+