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 Easy_install/PyPi installations are not

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 script::

    svn checkout obspy-svn
    cd obspy-svn/misc/scripts

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:

Best regards,