First steps towards a proper implementation.

Created a class structure that right now can deal with waveform data.
Adding StationXML more or less works.
Working StationXML adding and some other bugfixes.
Removing old code.
Added __str__() method.
Helper class for accessing the waveforms.
Convenient access to waveform files.
Correctly attaching metadata to new trace object.
Added nice interface to access the inventory information.
Starting to add the processing functionality