database: datetime to time epoch

* Convert all the time operation to work
  with epoch instead of datetime. It
  improves performances. And simplify the
  code.

* Add some function to get project conf
  in function of a date parameter.

Signed by: PXke
templates : templates now works correctly with time epoch

* Adapt the differents templates to make them work
  with the new time system.

* Logging part now show the time with the local time.

Signed by: PXke
web_app : routes for projects, time server and more

* There is now a route to ask the server its internal time.

* The route to ask for projects configurations is now
  made to accept date.

* And more ...

Signed by: PXke