Change default for `name` from `"_col=[N]"`

[gkellogg]

This value was originally established in the CSV2RDF spec, to generate column property identifiers if a column name is not established. The Metadata spec just picked this up as the default for name, which is then used to create predicateUrl if not established. However, this is unfriendly for many serialization formats unless escaped. Suggest to change to "_col.[N], where [N] is the row number. Examples using something similar for _row=[N] should be changed similarly.

@JeniT suggested something like this, but wanted to pass by @iherman and @6a6d74.

[iherman]

I do not have strong feelings about this, to be honest... if _col.[N] works for all serializations, it works for me...

[gkellogg]

Once other outstanding PRs are merged, I'll do this (without objection), as well as instances of #row= to use #row. in examples to avoid painful merge clashes.

[JeniT]

@gkellogg could you also update the description of the required syntax for name to allow .s please, because it should.