If urlgrab returns a URLError (for example if the Network is unreachable)
the for loop did not continue and the osc build aborts.
Now we also catch the URLError and try the next mirror and return False
correctly if no mirror could be reached. And then try to download it from
api
- simplified TextMeter/pb usage
- fixed header in meter.py
- delted unused vars in function calls
- get rid of most MGErrors
- do not check for file:// in grabber.py
* renamed mirror.py to grabber.py
* moved OscFileGraber Class to grabber.py
* in OscMirrorGroup we now use a OscFileGrabber class
* moved progressbar handling in own module (meter.py)
* simplified MGError
