Modified application to use only one layout

Application.php now uses only the structure.php
- Only one custom css needed
Modifications in header.php :
- when controller=home action=welcome, replace navbar with brand+login
button on the left.
Deleted unused css and js (previously used by custom login page
Binet selection menu moved from header to sidebar
Error line  35 : missing ) corrected.
Deleted unused files
Updated main CSS
New simple login page - bound to change
Corrections
Header updated : loaded only when user logged in
Solve conflicts
Corrected asset_path arror"
Undoing changes
Correction in header.php
identation corrections - created php tag
ready for pr
Merge pull request #20 from aymericbouzy/new-login-page

New login page