Prepare integration tests that cover at least the elements of `golem-core` containing bits from `yapapi`

[approxit]

As #54 identified yapapi bits, before further work in #57 we want to cover that very bits of code with integration tests, which will aid us significantly in later steps.

Todo:

• Prepare goth tests for code state of golem-core that still uses yapapi stuff.
  • Use only latest stable version of yagna

[lucekdudek]

After seeing results of #54 we decided that additional integration tests are not needed as working examples provide sufficient coverage of planned changes.