Feature/download multiple qr img at once

[0xRenegade]

This one is a bit bigger, but pretty simple.

• In both forms/dynamic_table.php and forms/static_table.php
• checkboxes to each table row, header row gets checkmark that selects all others in the table and visa-versa.
• Adds ajax to custom.js to call new backend file bulk_action.php in root folder
• bulk_action.php takes the selected qrcodes and gets their image name from the database, then creates a zip of all the images in a new folder called 'zip' that lives inside /saved_qrcode/ which use this naming convention:
• /zip/qrcode_{$_SESSION['user_Id']}.zip and everytime they request a new zip, the previous one will be unlinked using this same naming convention before making a new one. as long as there's not duplicate user_id's then it shouldn't bug out.

After zip is created, returns to ajax the url where it lives, then does a redirect with javascript of that url to download it.

[giandonatoinverso]

I looked at the code you proposed. Good job.

Thanks for contributing to the project!