sql.py: Added reconnect()

sql.py: DbConn._reset(): Assert that _savepoint is 0 instead of setting it to 0

db_xml.py: put_table(): put_table_(): Removed no longer used limit, start params

db_xml.py: put_table(): Merged partitioning and subsetting into same section for simplicity, to avoid creating extra temp tables, and to later allow the connection to be closed and reopened between partitions. partition_size: Expressed value without exponent notation to ensure that it's an integer.

db_xml.py: put_table(): Partitioning in_table: Adjust bounds of last partition to actual row #s included

sql.py: DbConn: Added _ to reset() to indicate that it's a protected method and users should not call it directly

sql.py: DbConn.close(): Reset the connection completely using reset()

sql.py: DbConn: Added clear_cache() and reset() and use reset() in init()

bin/map: Use new DbConn.close()

sql.py: DbConn: Added close()