Change AssetStatus.used status description to more readable
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 pull request #516 from quamilek/change-status-name

Change AssetStatus.used status description to more readable
Merge branch 'develop' into feature/prepare-endpoints-for-racks

Conflicts:
	src/ralph_assets/tests/utils/assets.py
Merge pull request #507 from ar4s/70-rack-in-search-form

Added rack, data center, server room to search conditions
Many commits: because travis has trouble with building.
Merge pull request #515 from kula1922/feature/prepare-endpoints-for-racks

Entrypoints for visualization datacenter