Dataset common settings

## Background
There are some settings that would be useful to be defined as properties of a dataset.

## Feature
Allow to have properties to be defined for datasets, similarly as fields have _metadata_

## Example
Some metadata of the fields would be nice to be able to define only once per dataset, because the chance all the fields share them is high.
Good contenders:
* Time zone
* Locale
* Decimal symbols
* ...