- new module: Common
 - one table for all elections, and one table per election for votes
 - for now, forget about election_shortcut service
 - in production, the server only uses Ocsipersist
 - "<load>" directive in configuration file to load the Ocsipersist
   database from the filesystem at initialization time

 * max can be int or null
 * votes.json can be absent
 * incidentally, fix verify_partial_decryptions

 * one directory per election, indexed by uuid
 * elections.json is generated by run-server.sh

This is a side-effect of using a more recent version of Lwt. Now,
we're using Debian packages from experimental.

 * single files with all (raw) elections and votes
   - one line = one object
   - intentions:
     + elections are directly served from elections.json
     + new votes are directly appended to votes.json
 * other data (for now, keys and results) are put in separate files
   for each election

FIXME: mysterious segfaults happen in the toplevel, only there and non
deterministically... looks like a bug in Lwt: gdb and "thread apply
all bt" reveal that caml_interprete is running in two threads at the
same time.

Use more abstract datatypes where possible:
 * Helios_datatypes_t.election
 * Uuidm.t

Move user reference to Helios_services so that it can be queried from
templates.

This directory reproduces the virtual tree under static/ in
helios-server. It is a merge of */media directories from helios-server
sources. See urls.py for the mapping.

 * new module StdExtra, for things that are like they could be in
   stdlib
 * new module ElGamal, for "abstract" crypto stuff
 * check group parameters (p, q, g) in make_ff_msubgroup
 * check that q is prime