Entrypoints for visualization datacenter

- Added entrypoints as api. Using django rest framework
- Created new place named `rest` for all django rest framework stuff
- Added tests and routing insite `rest` folder
Merge branch 'develop' into feature/prepare-endpoints-for-racks

Conflicts:
	src/ralph_assets/tests/utils/assets.py
Merge pull request #515 from kula1922/feature/prepare-endpoints-for-racks

Entrypoints for visualization datacenter