* Allow tweaking of the index that MySQL use when searching products
Sometimes when working with large dataset with many entities the MySQL engine does not pick-up the right index.
This is especially true when doing a search over the reference because the LIKE '%%' prevent the uk_product_label from being chosen.
This PR aims to improve this situation by doing the following :
- Adding a simple index on entity column.
- Adding an hidden constant to force the index being used when searching products.
Performances over a 8M products dataset shows a reduction of 2/3 execution time.
* Add missing global $conf
* Fix wrong usage of getDolGlobalString()
* Finalise fix
* Add more indexes
* Rework indexes
0cfd16d8db