Class name autocompletion in the middle of the value in xml services

[stof]

When I'm tryign to change the class name of a service defined in XML, the only way to get autocompletion is to put the cursor at the beginning of the class attribute. and then, the autocompletion leaves the existing content after the autocompleted one, whcih makes it broken.
This is totally inconsistent with the way the PhpStorm completion works.

If I put the cursor in the middle of the existing value, I would expect to have the autocompletion being triggered based on the text on the left of the cursor, and having the text on the right be replaced when hitting Tab to apply the completion

[Haehnchen]

#327 possible side effect

[Haehnchen]

did some improvements by time here