Create class for household assets

[aellenhicks]

Proposed definition by zhengj2007 in issue #62

household assets: An information content entity about items that a household owns such as a car, funiture, etc. (parent: IAO_0000030 information content entity)

[aellenhicks]

How about the prosed label and definition?
'household asset data item' - A socio-economic data item about the possessions of a household that have monetary value.

If data item is too specific, we can change to information content entity.

[cstoeckert]

Yes this works (see related #66) comment about assets.