"Remember me" feature of the login

*Title: "Remember me" feature of the login.

*Documentation:

Standard checkbox "Remember me" has been added on login page.
If an user wants to store current session (not login/password) to the cookie
should click on the checkbox.
After that user will automatically login on site without entering login/password 
every time (if cookie has not been expired. See site.ini.[Session].RememberMeTimeout)

If site.ini[Session].RememberMeTimeout is empty or 0 this ability will be disabled.

New INI setting in site.ini has been added:
- [Session].RememberMeTimeout:
  Number of seconds a session cookie will last,
  Empty or 0 means this ability will be disabled and CookieTimeout will be used.