[web/request] simplify search_state loading, fix comment

[webrequest] Lazy-load search_state - The update_search_state function will hit the session data only if __mode is present in the form. - set_search_state keep the same semantics - Direct access to search_state in the session data is changed by an access to the new property. Closes #4875761

[config] disable fckeditor by default (closes #1368900) FCKEditor is no longer maintained, and has a history of XSS issues. Let's use plain text as default text format.