hopefully doesn't break in the other browsers

Please someone who know the code, double check this one.
It does look that translation for 2 options were missing.

IE doesn't like it when you create a DOM element in one window and
try to insert it in another window.

Resolves #1192

`/lib/plugins/<plugin>/deleted.files`
which list files that can be removed e.g.
```
# This is a list of files that were present in previous plugin releases
# but were removed later. An up to date plugin should not have any of
# the files installed
action.php
folder/file.txt
```

* improved spacing of popup
* made primary buttons clearer
* xhtml and validity fixes
* improved some lang strings
* moved 'open as popup' after intro
* fixed page reload after clicking 'open as popup' button

Выравнивание и разбиение по образцу en/lang.php, унификация "директорий" и "папок", "расширений" и "дополнений"

however I think I will convert the dialog to a real popup instead.

In line 5 and 6, Message have two spaces, so I change them to a space.