[Tock Studio] Handle namespaces in state service + refresh dialogs on app change + misc

[rkuffer]

• Namespaces retrieval management is delegated to the state service. In this way, the namespace list selector in the application header is updated when a new namespace is created.
• Some competing requests made during application initialization are avoided
• List of dialogs in Analytics > Dialogs view are refereshed when configuration change
• Make sure that takeUntil is always the last operator of subscription pipes through the application
• Poorly managed subscriptions corrected on certain components (work to be extended to the entire app)
• Correction of a case not correctly handled in the destruction of the Sentence-training component
• Prevent spinners from being displayed over the application header

[assouktim]

Thanks a lot!