[FR] Next activities

[vladnew27]

User story 1 :
As a user I want to be able to add for my each activity my next activities, I most likely will start after current activity.

User story 2:
As a user ruining activity
I want to have my next activities of current one to be at quickest access
So that I spent less time and attention on finding my next desired activity

User story 3:
As a user
I want to see toggle "show only next"
So that I can see only my next activities in the notifications (see screenshot)

User story 4:
As a user ruining activity
I want to see recommendations for next activities, provided by the app based on my statistics