History: Plugin Alias Handler

            This is a ((handler)) to use a ((doc:plugin alias)), created from profiles.

!Sample
{CODE(caption=>YAML)}
objects:
 -
  type: tracker
  ref: tracker
  data:
   name: Hello World
 -
  type: tracker_field
  ref: only
  data:
   name: Only Field
   tracker: $tracker
   type: text_field
   flags: [ searchable, public, list, mandatory, link]
 -
  type: plugin_alias
  ref: my_alias
  data:
   name: mytracker
   implementation: trackerlist
   description:
    name: My Tracker Plugin
    description: Does nothing meaningful, just testing profiles
    prefs: [ feature_trackers ]
    params:
     foo:
      name: Foo
      description: Bar
      required: true
   body:
    input: use
    default: Hello World
   params:
    trackerId: $tracker
    fields: $only
{CODE}

! Plugin Alias Object
The plugin alias object is mapped directly to the internal structures. Because there are multiple nested structures, multiple tables are used to describe it.

||__Field Name__|__Mandatory__|__Value__
name|y|The name of the plugin, must contain letters only.
implementation|y|The name of the underlying plugin.
description|y|Equivalent of a plugin info function return value. Used to generate the documentation.
body| |Complex structure, described below
params| |Complex structure, described below
||

!! Body
This section describes what to do with the body of the plugin. The body may be passed through to the implementation or a custom body can be sent instead. Parameters may be contained in the body, like ~np~ %name% ~/np~".

||__Field Name__|__Mandatory__|__Value__
input|y|use or ignore, what to do with the user input
default|y|Value to send if user input is empty. 
params| |List of replacement parameters, described below
||

!! Plugin parameters
Plugin parameters are identified by a key (the parameter that will be provided to the implementation plugin). The parameters can be provided in two forms:

name: default value

or

name: complex structure, where structure is described below

||__Field Name__|__Mandatory__|__Value__
pattern|y|String to provide to the plugin with possible parameters
params|y|List of replacement parameters, described below
||

!! Replacement parameters
Each replacement parameter is identified by a key (used to replace with) and the containing values are as follow:

||__Field Name__|__Mandatory__|__Value__
input| |Name of the parameter to read from, if different from the token name
default| |Default value to replace with if parameter not provided
encoding| |none, html or url , the encoding type to use when replacing the value
||