sql.py: DbConn.run_query(): When debug logging, label queries with their cache status (hit/miss/non-cacheable)

sql.py: DbConn.run_query(): Also debug-log queries that produce exceptions

sql.py: DbConn: Allow creator to provide a log function to call on debug messages, instead of using stderr directly

bin/map: Pass debug mode to DbConn so that SQL query debugging works again

sql.py: DbConn: DbCursor: Fixed bug where caching was always turned on, by passing the cacheable setting to it from run_query(). Turned caching back on (uncommented it) since it's now working.

bin/map: map_rows()/map_table(): Pass kw_args to process_rows() so rows_start can be specified when using them. DB inputs: Skip the pre-start rows in the SQL query itself, so that they don't need to be iterated over by the cursor in the main loop.

bin/map: Fixed bug introduced in r1718 where the row # would not be incremented if i < start, causing an semi-infinite loop that only ended when the input rows were exhausted. process_rows(): Added optional rows_start parameter to use if the input rows already have the pre-start rows skipped.

input.Makefile: Sources: cat: Changed Usage message to use "--silent" make option

input.Makefile: Sources: cat: Added Usage message with instructions for removing echoed make commands

run_*query(): Fixed bug where INSERTs, etc. were cached by making callers (such as select()) explicitly turn on caching. DbConn.run_query(): Fixed bug where cur.mogrify() was not supported under MySQL by making the cache key a tuple of the unmogrified query and its params instead of the mogrified string query. CacheCursor: Store attributes of the original cursor that we use, such as query and rowcount.