Avoid continuing when RS has no sensible shard.

Since RS has a different arg parser than most other services, a
difference slipped in: when the shard was not specified and could not
be autodetected, RS did not exit immediately.

Added also a check that the specified shard is in the configuration,
and some unit tests.
Fix RPC server not starting in WebServer

Due to name collision.
Fixed tex escaping
Add cmsPasswordSlips utility
nl translation.
fr translation.
Several fixes after reviews from Victor.
Improve cold-start performance of RWS

And suppress lots of warnings.

By loading subchanges in order we will only append to lists, which is
way more efficient than resetting the per-user/per-task history each
time.
Fix bug in have_changed to output_only task

When a contest contains output_only task, cmsReimporter throws an error
such that sol is not found.

Fix it by adding if-statement that checks task type.
To achieve it, initialize conf.
Add contributor
Add Japanese translation
Remove duplication of allow_questions and allow_communication
Fixed bugs on on_connect_handler not sending a parameter.

With the reorganization of cms.io, the parameters (remote service
coord) sent to the on_connect_handlers went missing causing crashes
when triggered (only when a worker went offline and online again).
Merge branch 'master' into germany-master