[FIX] stock: move analysis report incorrectly merges multiple lines with same picking...

[FIX] stock: move analysis report incorrectly merges multiple lines with same picking, product and qty

This error probably stems from the useless complexity of
the SQL view declaration and the double GROUP BY levels.

The patch rewrites the view query with a single GROUP BY
level and proper aggregation levels, but the core part
of the patch is to replace the outer `group by product_qty`
with a `sum(product_qty)`.

Some columns were also mentioned twice in the same GROUP
BY clause, for some reason.

bzr revid: odo@openerp.com-20131025103626-7l78kdjjr7c2wesb