refactoring the repository structure, new svn checkout

Dear Users,

this email only affects users who have installed the development
version of Obspy via an svn checkout followed by the
develop.sh/develop.bat. Easy_install/PyPi installations are not
affected.

In order to allow efficient branching via svn switch and the tagging
new releases, Robert and me refactored the repository structure.

Please remove your current obspy-svn installation, checkout only
the trunk of the repository and rerun the develop.sh/bat script::

    svn checkout https://svn.obspy.org/trunk obspy-svn
    cd obspy-svn/misc/scripts
    bash develop.sh

The branches or tags will contain a lot of server-side hardlinks in
future versions, which would resume a lot of space on the client PC.

I updated the corresponding document:
https://obspy.org/wiki/SVNInstallation

Best regards,
Moritz