Move source code to a separate directory

[thorin-schiffer]

Currently, the source code is placed on the same level as the rest of the files. This can be a big impediment in splitting the things from each other and also makes the root of to be looking quite messy.

There is future plan of splitting the acceptance tests deps from the rest of the repo, as they are completely different and quite heavy, this is the first step in that direction.

While splitting check if the following functionality is not broken:

• docker support, docker image is building and running
• unit tests are running
• acceptance tests are running
• circle ci pipelines are working
• heroku Procfile is correct
• invoke routines are working correctly (check inv bootstrap for example)