Better 'makeproductgroups' handling.

* Do not insert group into all products by default when 'makeproductgroups' is on
* Allow to choose whether to create access group for new products
* Move group and series creation calls away from Product->create
* Change help text
* Enable makeproductgroups by default again
Redesign bug edit form.

* Use "label \n field" instead of "label \t field".
* Use divs instead of tables for layout.
* Make page scale from 4 columns down to 2 and then to 1 using media queries.
* Reflow 4 custom field columns with JS to balance their height.