Headless mode implementation

[OlesiaSub]

There are a few problems that I still haven't solved. For instance, random Execution exceptions (they are the reason for re-launching the program in a cycle). The reason why they are thrown is that mock python sdk is not created on time, so an exception is thrown when it is queried from some inspections (such as redundant print and sleep ones). Second major problem is connected with defining current file's test runner. It works fine (hopefully), however it is really slow and probably not correct in sone cases (for example when there are two frameworks imported in one file). Moreover, my code has lots of duplicate fragments. I'm not sure how to get rid of them yet.

As for README - I experienced an issue when I tried launching headless from the command line. The issue is connected to conflicting Java versions used by main application and plugin-utilities. Unfortunately, I was unable to fix it, hence I only described the process of launching headless mode from ide.