LDEV-1912 set session timeout programmatically according to lams' UserInactiveTimeout value via a servlet listener rather than hard coding to 120 mins (in some webapps, no session timeout was specified at all).
LDEV-1255: Moving the code for stopping jsps caching to a new custom tag, so that it can be applied consistently across all pages. Moved the utf-8 statements to the same tag so we don't have to remember to put them in all pages.