[schema / sources] store data sources as cubicweb entities this implies several changes: * new CWSource / CWSourceHostConfig entity types * only the system sources and default admin login/password stored in sources file (other stuff will be ignored) * on startup, get sources definition from the database * every entities have a cw_source relation * a facet allow filtering

function set_tab(tabname, cookiename) {
    // set appropriate cookie
    loadRemote('json', ajaxFuncArgs('set_cookie', null, cookiename, tabname));
    // trigger show + tabname event
    trigger_load(tabname);
}