Improve sessions.sql
Improve sessions.sql

* more strict types
  - table => utf-8 charset
  - primary-key => ascii_bin
  - data => blob
  - expires => unsigned & could in theory be set to NULL (does not expire)
* added created and modified which are set automatically without having to create the table object (but you can and the DatabaseSession handler will take a `SessionsTable.php` if it can find it). These fields help with server side invalidation.
QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp