Fixed SQL query in Cart.php

- Fixed SQL query which updated duplicated product quantity when it has customizations
Updated SQL query variable in Cart.php

- Fixed quantity merge variable at line 3325; Correct variable is non-array at line 3311
Fixed customization duplication in Cart.php

- Replaced invalid nested SQL query with working DB methods. Duplicating cart products with customizations will not throw an exception now.
Added quotes to SQL query column

- Column name `index` is reserved, needed quotes
Moved last ID variable line to proper place

- move last insert ID line to the right place so it saves the variable correctly;
Merge branch '1.6' of ssh://github.com/gskema/PrestaShop into gskema-1.6

Conflicts:
	classes/Cart.php
Merge branch 'gskema-1.6' into 1.6