[book] Improve PostgreSQL configuration section
* Do not advice for specific PostgreSQL version (point to meta-packages if
available in Linux distros);
* First mention packages from Linux distros, put the link to official postgres
documentation at the end;
Closes #2725302.
[js] add a selector string escaping function
will help use id strings in jquery selector expressions, e.g:
"foo.[subject]:42" -> "foo\.\[subject\]\:42"
Related to #3154531.