Data type: keyword parameter type

--Overview--

A type of parameter that can be used in a [[type:keyword]].

--Properties--
! Property		Type					Default		Description
| @name@		[[type:string]]				''required''	Name of the parameter type.
| @description@		[[type:string]]				''required''	Description of the parameter type.
| @placeholder@		[[type:string]]		@name@ of this param type	Placeholder to use for empty parameters, the name is used if this is empty.
| @optional@		[[type:boolean]]			@true@		Is a placeholder used when a keyword is encountered with no parameter,<br/> for example @"Cycling "@ would become @"Cycling <atom-kwpph>cost</atom-kwpph>"@.
| @match@		[[type:regex]]				''required''	Regular expression that this param type matches.
| @separator before is@	[[type:regex]]				@""@		Regular expression of separator before parameters of this type.
| @separator after is@	[[type:regex]]				@""@		Regular expression of separator after  parameters of this type.
| @eat separator@	[[type:boolean]]			@true@		Allow the user to 'type over' the separator.<br/>
			 					 		For example if the separator is @" "@ in the keyword @"Cycling"@, and the user types @"Cycling"@,
			 					 		a space and a placeholder is automatically inserted, making @"Cycling <cost>"@.
			 					 		If the user now presses space the cursor is only moved, no additional space is inserted, the space is 'eaten'.
| @script@		[[type:script]]				 		Script to apply to parameters of this type before substituting them back into the text.
| @reminder script@	[[type:script]]				 		Script to apply to parameters of this type before using them in the reminder text.
| @example@		[[type:string]]				 		Example for in the keyword editor, currently not used.
| @refer scripts@	[[type:list]] of [[type:keyword param reference script]]s
			 					 		Scripts for inserting parameters of this type into the reminder text.
			 					 		To make this easy for the user, a menu of ways to use a parameter is provided.

--Example--
The 'number' parameter type. It matches a sequence of digits.
It can be included in the reminder text directly, or by applying some function first.
>keyword parameter type:
>	name: number
>	match: [0-9]+
>	refer script:
>		name: normal
>		description: (1,2,3)
>		script: \{{input}\}
>	refer script:
>		name: as words
>		description: (one, two, three)
>		script: \{english_number({input})\}
