Csv import changes

Added tests & updated factories.
Fixed data importer bugs:
- importing barcode with value ''
- importing data for fields:
    - LicenceType
    - Service
    - BudgetInfo
    - ServiceCatalog
    - DeviceEnvironment
    - AssetOwner

- AttributeError for category field (api_ralph)

Data importer improvments
    - getting data from field of types: BooleanField, DateTime, Date
    - added delimiter guessing
    - col 'id' in import-update can by anywhere (before only first col)
    - adding new assets tries to match device by this chain: barcode then sn