picking in obspy.core.stream object Qt frontend

Hi guys! :)

after looking for a decent picking program last week, the only good option I found was ObsPyck which is kind of a big suite and unfortunately doesn't fit well into an existing ObsPy environment.
I decided to take a couple days, get into Qt and throw together a leightweight picking GUI, interfacing ``obspy.core.Stream`` and the ``obspy.core.event`` API (therefore QuakeML).

IMO these objects are far more easy to handle than any abstract text format like from sac or PQL.

* Reading ``obspy.core.Stream`` and ``obspy.core.event.Pick``

```python
cat = readEvents('events.xml')
new_pick = st.pick(picks=cat[0].picks)

print new_pick.picks
>>> obspy.core.event.Pick() object
```

* Saving/reading QuakeML files through the interface, saving plot as image.

* Stream's slides are grouped by stations name (3C per slide)

![streampick-gui](https://f.cloud.github.com/assets/4992805/1046180/8ddfdd9a-1034-11e3-9d93-3f882c1d4e44.png)

![streampick-about](https://f.cloud.github.com/assets/4992805/1046181/96b713fc-1034-11e3-933a-7e0cb0603623.png)

The question for me is now whether you want a Qt module in obspy.

cheers,

Marius