improve restartFx function

* start observation and timer, then try to update session
* update alert dialog message
declare constant for embedded delay time
update styles of Google result page

* remove redirection to the simple mode images page
* optimize CSS setting
make regexp to match replacements in no particular order
support Unicode strings for string type prefs
remove |try catch| to know errors of wrong settings
implement setImmediate

* this is an experimental feature
* used instead of the setTimeout(fn, 0)
* see https://developer.mozilla.org/ja/docs/Web/API/Window.setImmediate
minor fix

* remove missing URL
* add TODO comment