Most all Drill format plugins allow the user to configure various options for that plugin as part of the format config. The one glaring exception is the JSON reader which has several configuration options which can only be set globally. This PR moves these to the format config so that users can set these options when they configure a storage plugin.
This PR does not eliminate the global settings for JSON. It simply adds another place where a user can update the settings. If the settings in the config file are not defined (`null`) Drill will use the global settings.