Standardize descriptions for properties

[peterdesmet]

Throughout the specs, properties are described with different phrasing:

Short: https://datapackage.org/specifications/table-schema/#title

title

A human readable label or title for the field

Explanation first: https://datapackage.org/specifications/table-schema/#uniquekeys

uniqueKeys

A unique key is a field or a set of fields that are required to have unique logical values in each row in the table. It is directly modeled on the concept of unique constraint in SQL.

The uniqueKeys property, if present, MUST be a non-empty array. ...

Verbose: https://datapackage.org/specifications/table-dialect/#header

header

A Table Dialect descriptor MAY have the header property that MUST be boolean with default value true. This property indicates whether the file includes a header row.

I think this should be standardized throughout. I'm not a fan of the verbose description, but would indicate if a property is required or not as part of the heading (cf. https://datapackage.org/specifications/table-schema/#name)