events on toolbar for mode change and date change

[VamsiKrishnaMyneni]

we have scenario where we need events on mode change(day, month, week) and on current month change.

[VamsiKrishnaMyneni]

@rouftom can you please accommodate it

[VamsiKrishnaMyneni]

we are having some scenarios as below

1. we need an event on mode change which gives us value what is the current mode selected and what was the previous mode.
2. we need an event on toolbar date change which gives us value what is the current selected date and what was previous date.
3. we need an default current date prop to set the default selected date
4. we need an ability to configure the required modes only.(we have scenarios where we need month, week sometimes and other time day, week).
   @rouftom could you please accommodate the changes which fulfils above scenarios.