Implement resource leveling feature

[arcady-zherdev]

Requested here:
https://www.bryntum.com/forum/viewtopic.php?f=52&t=18285
https://www.bryntum.com/forum/viewtopic.php?f=52&t=18371
https://forum.bryntum.com/viewtopic.php?p=119502#p119502

[taauntik]

+1 user asked for the similar FR

[canonic-epicure]

Another request here

[marciogurka]

+1