added new default accessory
changed API for visualization blade chassis
Added constraint slot_no cant be set when asset is no blade + tests
Merge pull request #539 from xliiv/block-slotno

block slot_no if asset not blade
Merge pull request #545 from ar4s/fixtures-added-power-socket

Added new default accessory
Merge pull request #544 from ar4s/visualization-blade-chassis

Changed API for visualization blade chassis
WIP