added FT class which is used in Model::field() methods

FT class has following types:
   enum FieldType
   {
	default_type = 0,
        primary_key = 1,
	foreign_key = 2,
	foreign_key_in_child = 4,
	no_insertable = 8,
	no_updatable = 16,
	no_fetchable = 32, /* not supported yet */
   };
an object of FT class are now used in Model::field() methods instead of insertable/updatable/is_primary_key/... boolean flags

changed the semantic of has_foreign_key (which was a bool) flag in child Models:
now on Models and list/vector of Models you should use either FT::foreign_key or FT::foreign_key_in_child
1. FT::foreign_key means that field with this flag is a foreign key and is pointing to the child object
   (it was the case when has_foreign_key was equal to true beforehand)
2. FT::foreign_key_in child means that the foreign key is in the child object and is pointing to the parent object

src/model.cpp

@@ -943,5 +943,25 @@ void Model::put_fields_to_log(PT::Log & log, const wchar_t * db_field_name, cons
 }
 
 
+PT::TextStream Model::log_table_name()
+{
+	PT::TextStream buf;
+	table_name(buf);
+
+	return buf;
+}
+
+
+PT::TextStream Model::log_table_name(const wchar_t * db_field_name)
+{
+	PT::TextStream buf;
+	table_name(buf);
+	buf << '.' << db_field_name;
+
+	return buf;
+}
+
+
+
 } // namespace