apvn support like accounting groups

common/proto/table_definition.proto

@@ -311,6 +311,8 @@ message ColumnDefinition {
   //   PHONE (international or national phone number; generates extension/type/country/calling-code companions)
   //   TIME (timezone-free time of day)
   //   MONEY (= unconstrained NUMERIC; currency is declared below)
+  //   STATEMENT_CLASS (A = assets, P = equity and liabilities,
+  //                    N = expenses, V = revenue)
   //   ACCOUNTING (creates schema-managed name, account, debit, and credit fields;
   //               account always selects a row from the profile's managed ledger_accounts table;
   //               name is limited to 10 characters and one stored row contributes