mseed: add test file for so far unsupported SRO encoding in miniseed
Adding support for SRO encoded MiniSEED files
Adding some more miniseed encodings.
Added definitions of unsupported encodings.
Proper errors for reading miniseed files with unsupported
encodings.
Removing 'recinfo' argument from readMSEED().

Does not break any existing code and the speed gain is
minimal in any case.
Better handling of encoding during writing.

Some encodings cannot be written with libmseed. Now raises appropriate
errors.
Test that the correct exceptions are raised
Also test setting the encoding via the trace stats.
Added test for the GEOSCOPE16_4 format.

The file has been downloaded and binary patched to fix an obviously wrong
header value and to reduce the record length to 512 bytes.
Renaming test file
Adding test case for the SRO format
Compat for Python 2.6
Reworked the obspy.mseed documentation.
Adding test for the DWWSSN.

The test file is from IRIS and has been manually patched to have a
shorter record length.
Added test for the CDSN encoding.
Merge branch 'master' into mseed_sro_encoding

Conflicts:
	obspy/mseed/headers.py
Merge pull request #835 from obspy/mseed_sro_encoding

miniseed: support for (legacy) SRO encoding