* fixed PyTorch caching
* added ccache to CI
* broke habitat api step on installation and testing to save extra 5 min on saving cache in parallel
* testing time drops from first run to second run from 17.5 minutes to 9 minutes (2x times) for full testing.

* Add fog-of-war to topdown map

Added installation requirements step for sim installation in CI setup

Added description how to use config system, fixed missing copyright headers, improved example and isort CI (#125)

* Added description how to use config system related to #20.
* Added missing copyright headers
* Improve registry example to be cleaner
* Adde habitat_sim as first party lib to isort CI setup

* Made isort for CI check only

* Added badges

* Builds and installs habitat-sim with python setup.py install
* Added pytorch installation and running habitat baseline test in prediction mode. That maybe too much of testing, but decided to keep it for now.
* Have ideas how to speed up and parallelize jobs. Will follow up in next PRs.
* Run isort and black on whole code to make it happy.
* Includes parallelization of installation steps and use files as flags that step is finished. CircleCI has no good way to parallelize steps and have dependencies one the same machine.
* Cache is used to save conda dependencies installed and build simulator based on commit SHA.