sql.py: put_table(): Added support for putting just a window subset of the rows in the table. Removed "SELECT statement missing a WHERE, LIMIT, or OFFSET clause" warnings.

sql.py: put_table(): Return the column where the pkeys are made available (the out_pkey) instead of taking it as an argument

sql.py: put_table(): Get input pkeys corresponding to rows in insert and join together out_pkeys and in_pkeys into final pkeys table

sql.py: put_table(): Fully support multiple in_tables, joined together using the main input table's pkey

sql.py: mk_select(): joins: Fixed bug where USING-based joins did not have closing ")"

db_xml.py: put_table(): Fixed bug where in_table was last in in_tables instead of first, causing it to be ignored by the current put_table() implementation, which only considers the first table name

db_xml.py: put_table(): Fixed bug where pkeys_table returned by recursive call to put_table() needed to be prefixed with $ to be treated as an input column name rather than a literal value

sql.py: mk_select(): Support joins with USING, which can be used to merge multiple input cols into the same output col

sql.py: mk_insert_select(): embeddable: Fixed bug where query that uses function was being sorted by its first column (the default mk_select() setting), when it should be left in its original order

sql.py: put_table(): Take a dict mapping out to in cols instead of separate in and out cols lists