strings.py: Added as_code()

sql.py: DbConn.run_query(): Prepend "DB query" before the query debug message so it can be identified as a DB query

db_xml.py: put_table(): Subset in_table: Document that in_table will be shadowed (hidden) by the created temp table, rather than versioned, now that the table is (almost) always created as a temp table

sql.py: Create temp items as permanent in autocommit mode rather than in debug mode so that temp items are only permanent if actually committing result. This ensures that the generated SQL in test mode matches what would actually get run in regular commit mode, and the SQL is only altered to make the temp items visible if actually debugging (autocommit mode).

sql.py, sql_gen.py: Reformatted generated SQL for presentability by adding newlines

sql.py: DbConn.run_query(): Put a newline before the query in the debug message so that multiline queries have all rows at the left edge rather than the first row prefixed by other text

sql.py: DbConn.run_query(): Don't put generated query debug message all on one line, so that embedded newlines are preserved

sql.py: Fixed bug where queries with versioned identifiers which threw an exception (not related to name collisions) were being output with a too-high log_level, because all exceptions were output with the higher exc_log_level, by making the following changes: DbConn.run_query(): Changed exc_log_level param to log_ignore_excs param so that only certain exceptions would cause the query to be output with a higher log_level. Moved the code that actual emits the query debug message from DbConn.run_query() to module-level run_query() so it would apply the log_ignore_excs filter after the exception had already been parsed into specific types.

Moved "Putting columns" debug message from db_xml.py put_table() to sql.py put_table() to put it in the same place as the other debug messages

sql_gen.py: Added remove_col_rename() and use it where `if isinstance(value, NamedCol): value = value.code` was used