Add option to define common fields for all blocks

[piotrpog]

What would you like to see added to or changed in Neo, and why?

Lets say every of our blocks needs to have some field, for example padding bottom/top or background color.
Would be useful if we set these fields in one place for all blocks, instead of adding them into every block manually.
These fields could be displayed in to separate tab, appended automatically to existing tabs in the field layout of every block.