[Olena] Snapshots from BuildBot

BuildBot has been producing snapshots for a while (long before we switched from Subversion to Git), which were compiled from the main development tree (SVN's trunk at the time), and uploaded here: http://www.lrde.epita.fr/dload/olena/snapshots/ However, now that we use Git, it seemed pointless to keep the same mechanism: each commit in /any/ branch ending in a successful build would produce a tarball overwriting the previous snapshot, whatever branch were used in the production of the later. So I adjusted the lrde-build.sh script used by BuildBot to 1. Filter the branches producing a snapshot after a build successfully completed. Currently, these branches are `master', `next' and `swilena'. Ask me if you want to add more branches to this set. 2. Have snapshot be stored in a subdirectory of the previous URL, e.g. http://www.lrde.epita.fr/dload/olena/snapshots/next/ http://www.lrde.epita.fr/dload/olena/snapshots/swilena/ ... This way BuildBot won't overwrite a snapshot with changes on Scribo with, e.g., a snapshot with changes changes on Swilena. The generated documentation is also stored in the subdirectory, as usual. The names used for the tarballs are a bit lengthy, but this removes any ambiguity as for their content IMHO.