Merge tag '0.15' into develop

* Enhancements
  * [#126] Use grammar v2
* Bug fixes
  * Duplicated `parametersVersion` between `ProfileStorage` and `ParametersStorage` (leading to bugs)
Remove useless questions.json
Clean up ParametersStorage
SchedulerService now actually uses grammar-v2 parameters!

It also aborts if parameters haven't been received yet. SyncService
calls it when parameters are updated.
Merge pull request #151 from daydreaming-experiment/feature/grammar-v2-fixes

Feature/grammar v2 fixes
Bump version
Update GRAMMAR-VERSIONS
Update CHANGELOG
Merge branch 'develop' into hotfix/0.15.1
Delays are given in seconds in the parameters
Merge branch 'hotfix/0.15.1'

`schedulingMinDelay` and `schedulingMeanDelay` were ignored in
parameters.