* Start single client session based on the default kernel or saved kernel in NB.
* Added kernel displayName to standardKernel.
Modified name to allign wtih Juptyer Kernel.name.
So we can show the displayName during startup and use the name to start the session.
* Change session.OnSessionReady event in KernelDropDown
* Added model.KernelChnaged for switching kernel in the same provider
* Fixed session.Ready sequence
* Fixed merge issues
* Solve merged issue
* Fixed wrong kernel name in saved NB
* Added new event in Model to notify kernel change.
Toolbar depends on ModelReady to load
* Change attachTo to wait for ModelReady like KenelDropDown
* sanitizeSavedKernelInfo to fix invalid kernel and display_name. For example: PySpark1111 and PySpark 1111
* Added _contextsChangingEmitter to change loadContext msg when changing kernel
* Resolve PR comments
118d2c7273