Remove all specific staff to the separate files (better plugins)

[GoAlexander]

The best method to fix this issue is to use plugin architecture.

What I mean "specific"? As I reviewed the code I can divide it into 2 groups:

• MediaSDK project staff (for example build options)
• Architecture`s personal staff (who said that number of stages should be hard-coded?!)

[GoAlexander]

@azhogov
I think the logic of stage should be closer to pynt`s task?
http://rags.github.io/pynt/

In opposite it should be as stage in gitlab?

I try to find use-case of current stage logic in non-buildbot systems...