Change AssetStatus.used status description to more readable
added rack, data center, server room to search conditions
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
fix: updated tests after factories update
Merge pull request #1 from xliiv/arek-rack-search

fix: updated tests after factories update
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
Added without_assisgned_location field to dc-search form.
Enables to search dc-assets without location fields.
Location fields are: data_center, server_room, rack, etc.
Merge pull request #520 from xliiv/no-location-in-search-ok

Added without_assisgned_location field to dc-search form.
added empty devices in response
Moved slot validation to view.
Better var name: asset_without_category_and_location.
fixed review sugestions
Merge pull request #521 from ar4s/feature/empty-space-in-api-rack

Added empty devices in response
Merge pull request #522 from xliiv/no-slot-validation-ok2

Moved slot validation to view.
- sync parent also for blase servers
- use slote_no instead position
- update info also for blade servers
Merge pull request #523 from andrzej-jankowski/sync

Location sync - changes
Added Accessory model + AccessoryType choice.
Moved device-info models to seperate file: models_device_info.py
added missing image to doc: doc/images/add-data-center-asset-form.png