datatables: Upgrade to 2.0.0 and update tables UI

This merge request upgrades datatables to version 2.0.0 and update tables UI as following:

• Remove scrollY option and use default behavior instead: when increasing the number of entries per page to display, it enables to scroll the page instead of scrolling a table of fixed height
• Add FixedHeader extension and use it: tt enables to have a fixed header when browsing a table with a large amount of entries per page
• Allow up to 1000 entries per page in some tables

Before:

After: