Fix mysql deprecation

[dhofstetter]

To be ready for using the recent php versions >= 7.0, we need changes in the mysql backend.

Installation routine

Just replaced the use of mysql backend functions with their appropriate opposite of the mysqli backend. I just did this for index2.php in the install folder. Their are multiple files looking very similar and I just used that file for my installation.

ReLiS App

I changed the remove_picture endpoints within Op and Manager Controllers, to use new functions within the Manage_mdl Model. There a db object gets obtained from codeigniter. This object provides the database specific escape routines. This change is solid against db Backend changes.