Fix: pathPrefix in ezpLanguageSwitcher

Problem:
When checking wether pathPrefix sould be removed or not, it was assumed that you already were in a subfolder of the PathPrefix. The case where you want to go to the root of your pathPrefix folder wasn't handled.

Ex:
- Home
  - *MyPathPrefixFolder*
    - News
    - Contents
    - ... 
  - MyOtherFolder

Let's say "MyPathprefixFolder" is the home folder for a siteaccess, then you'll have in your site.ini 
```
PathPrefix=MyPathPrefixFolder
```

When switching language directly from your homepage, the PathPrefix was added to the new language:
`mywebsite.com/switchlanguage/to/fr/` redirects to `fr.mywebsite.com/MyPathPrefixFolder` instead of just `fr.mywebsite.com`.

Oh and I also removed unrelevant params.
I might be wrong, but I thing the last "/" avoids special cases where a folder might start just as the pathprefix:

- Home
  - Pathpr
  - PathprOtherSA

I was wondering if this could be smarter to explode the url and take the first part of it, not sure if it's better in term of performance though.

I'll add those extra spaces ;)