[schema,server] add a security debugging aid (closes #2920304) - Add a DGB_SEC debugging flag (to be used with set_debug/debugged). - Add a context manager (tunesecurity) to filter security assertions. Note: this does not address all read-security mecanisms.

cubicweb-web: embedded-javascript-library usr/share/cubicweb/cubes/shared/data/jquery.js