Macro defining options that parametrize element.

It automatically generates appropriate struct and documentation.

Options are defined by a keyword list, where each key is an option name and is described by another keyword list with following fields:

• type: atom, used for parsing
• spec: typespec for value in struct. If ommitted, for types: [:atom, :boolean, :caps, :keyword, :string, :struct, :time] the default typespec is provided, for others typespec is set to any/0
• default: default value for option. If not present, value for this option will have to be provided each time options struct is created
• inspector: function converting fields' value to a string. Used when creating documentation instead of inspect/1
• description: string describing an option. It will be used for generating the docs