German "informal" language file

Note that the previous key "URL" has been changed to "full_url" to prevent problems with case-insensitive databases.
Updated English language ressource

Some minor typo corrections; key "url" was changed to "full_url" to prevent translation problems with case-insensitive databases.
Adapted "url" key

The key "url" was changed to "full_url" to prevent problems with the built-in translation support for case-insensitive databases (there is also a "URL" key).
Updated access to "url" key

In keeping with the changes in the language files, get_string('url', 'eduplayer') was changed to get_string('full_url', 'eduplayer')
Update eduplayer.php
German "formal" language file

Note: the key "url", which clashes with key "URL" on case-insensitive databases when trying to translate resources within Moodle, was changed to "full_url".
Improved translations

After experimenting, the stretching* strings were adapted to better explain the behaviour
Update eduplayer.php

Adapted descriptions of "stretching" to better reflect the behaviour.
Update eduplayer.php

Corrected a typo.
Merge pull request #3 from roessling/master

Updates: German translation and a bug fix for case-insensitive databases