Remove useless logging

The source code is public now...
Remove user_admin field

Each election may have an owner who can perform administrative tasks.
Refactor Templates
Move *_update_credential* to VOTING_SERVICES
Big overhaul of election management

Summary:
 - WEB_ELECTION gets a new submodule of type ELECTION_SERVICES
 - per-election services do no longer take UUID as a param, but are
   registered at a path containing it
 - no more ESIndex, election home service is back
 - inline some submodules of SITE_SERVICES, drop ALL_SERVICES
 - rename old SITE_SERVICES into CORE_SERVICES
 - move election-specific templates to a new ELECTION_TEMPLATES; the
   templates in the new signature do not longer take an "election"
   argument but TEMPLATES.Election is a functor that takes a
   WEB_ELECTION and returns an ELECTION_TEMPLATES
 - adapt the booth to the new path layout

Additional changes:
 - merge VOTING_SERVICES into ELECTION_SERVICES
 - inline {SITE,AUTH}_TEMPLATES into TEMPLATES
 - all templates take a final () argument to emphasize their impurity
Use a path relative to the booth for get-randomness