(this was for a custom prefix)
- removed column_prefix and column_prefix_index from BaseExpression
now we have a pointer to ModelEnv passed in field() method
- to ModelEnv: added table_name, table_name_simple and table_index
git-svn-id: svn://ttmath.org/publicrep/morm/branches/join_models@1193 e52654a7-88a9-db11-a3e9-0013d4bc506e