Added post_build_script to call scripts after user-defined build scripts

What does this MR do?

This MR adds possibility to define post_build_script that can be defined in config.toml just like pre_build_script but which is launched after user-specified build scripts were launched.

Why was this MR needed?

It is found useful to make administrative meta-tagging for deployed projects.

Are there points in the code the reviewer needs to double check?

Not really.

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?

Closes #2077 (closed)

marked the task Added for this feature/bug as completed

marked the task Added for this feature/bug as incomplete

I made tests on my local machine. All works fine.

@tmaczukin this is a tested MR for after_build_scripts for #2077 (closed) .

changed milestone to %v1.11

Now, after 2 weeks testing in production. All as expected.

Looks good :)

Thanks @seweryn.zeman!

merged