Fix in the doc, thanks to engelbert gruber.
Add dssi.register to dynamically register a DSSI plugin.
Add some log when registering DSSI plugins.
Added "stereo_mode" and "internal_quality" parameters for the %mp3 encoder.
Also load DSSI plugins from environment variables.

--HG--
extra : rebase_source : 16fc9f70fa4f3e86015a4b7ddc164322f22ce313
Added user and password to flows documentation.
Added syntax highlighting for all code snippets!
No need to add "@" for language part in %%
Fix test for MP3 internal_quality format.
Added g++ and libtool to deps.
s/interactive_float/interactive.float/g on dolebrai script.
Explain how to dump a stream in rotated files.
Faster generation of SVN.ml.
Fixed flush parameter type in output.external.
Added FAQ about temporary files.
BIG update of flows UI. Now serving flows page from the push app. Will investigate how to push it back to sf.net later.
Disable metadata override for fade.{initial, final}
Add decoder.taglib.force_mp3 configuration key to switch taglib metadata decoder to forced mp3 metadata decoding.
Fixed equality testing in list.remove
More general implementation of list.mem_assoc..