Option to keep all feature properties

https://github.com/mapbox/vtshaver/pull/20 landed the ability to have vtshaver automatically remove feature properties that are not needed for a given style.

However there are use cases (like querying) where some users might want feature properties to be kept.

A sophisticated solution for this would be to have vtshaver respond to metadata in the style that declares which properties to keep on which layers. However a more near-term solution I think would be to open up an option, exposed in the vtshaver CLI tool, that would disable all property shaving.

Start by reading the implementation from pull request #20 and locating the vtshaver CLI entry point. Trace where feature-property shaving is enabled, then add the requested CLI option to disable it. Done means users can keep all feature properties while the existing shaving behavior remains unchanged when the option is not used.

Written by the indexing model from the issue text.