Read/Write support for the DataAvailability tag in StationXML and update to FDSN WS 1.1

This PR adds read and write support for the `<DataAvailability>` tag in StationXML files.

It furthermore updates `obspy.fdsn` to support the 1.1 standard. It will still work with older implementations but it will complain about missing parameters which is fine in my book. The only real change to 1.0 is the addition of the `matchtimeseries` parameter.

I furthermore updated all test which starts to get annoying...
I guess a time span. Straight copy and paste from the StationXML scheme. Thanks a lot for all this proof reading by the way :-)