New view "directory" which display all entries in a list with datatables

[proxyconcept]

Enhancement (can resolve #19) :

• Add a new menu called "Directory" (with translations)
• Display all entries in rows and columns
• Integration of DataTables to sort and paginate
• Config option $use_directory to enable or disable this view
• Config options for displayed columns and default sort

[nqb]

There is also a link on each row to display entry (mentioned by @coudot in #16).

Other issues related : #1

[coudot]

Very nice!

We need to see if we can use the same for advanced search results when we use rows instead of boxes.

[nqb]

Very nice!

Agree with @coudot.

Remarks on this PR :

• sort icons should be more close than their column name to avoid sorting on bad column name
• no tel: or mail: links for each row (in comparison with quick/advanced search results)
• link on each row to display entry : will be nice to have a clickable row rather than an icon. Not so easy because we need to keep tel: and mail: links. Maybe a link on firstname/lastname.
• generalize display/pagination to quick/advanced search with rows (as @coudot said)
• number of elements display on pages :
  • add a PHP option to set default number (currently = 10)
  • add additional values in dropdown : "all" and/or an input field to enter a number (for example : 250)
• print preview is not usuable

[coudot]

We also need to add documentation on https://ltb-project.org/documentation/white-pages/0.2/start

@nqb could you do it once all required features are done?