Add 'name' property to links in collections

[bmayton]

The JSON+HAL spec notes of the optional "name" property of a link (§5.5):

Its value MAY be used as a secondary key for selecting Link Objects which share the same relation type.

This seems like it would be a useful way of identifying, from a collection of links, a particular device/sensor/etc. of interest. The "title" property effectively permits this now, however, the definition of the "title" property notes that it is intended primarily as a human-readable identifier. All present uses of the "title" property in collections of links in Chain do appear to be unique database identifiers for the resources they link to, but it seems like it would be more correct to actually implement the "name" property and key on that in client applications instead.