Draft: XML preprocessor

[MinyazevR]

Preprocessor of xml nodes before sending them to the Constraints Parser.
Syntax for defining a template:

<template name="template_name">
    <params>
       <param name="id"/> 
       <param name="param" default="true"/> 
       <param name="trigger">
	    <trigger>
	        <success/>
	     </trigger>
        </param>
    </params>
    <content>
<![CDATA[
    content
]]>
    </content>
</template>

1. Parameters can have a default value. It can be a valid sequence of xml nodes or set as a text string (via the default attribute). If both are set, the default takes precedence. In parameter declarations, you can use parameters from the initialization list above using the syntax #{}.
2. The template body must start with CDATA, and each parameter reference is processed using the #{} syntax, which is handled by regular expressions. This means that nested use of the #{} syntax is not allowed, and a separate parser is provided for such cases, which will complain if an undeclared parameter is used in the template body.
   Syntax for using a template:

<use template="templateName">
    <with id="123" param="false"/>
    <with param="trigger">
        <setUp id="my_id/>
    </with>
</use>

1. Parameters that are xml tags are specified using the with syntax with the param attribute, whose child is a sequence of valid xml nodes. Text parameters are specified using the with tag attributes, and parameters can be grouped in multiple with tags.
2. There is a simplified syntax that uses text parameters at the same level as the use tag without using with:

<use template="templateName"  id="123" param="false">
    <with param="trigger">
        <setUp id="my_id/>
    </with>
</use>

Templates can reuse other templates, that is, use syntax in their bodies to refer to other templates:

<template name="set-object-warzone">
    <params>
	<param name="regionId"/>
	<param name="objectId"/>
	<param name="message"/>
	<param name="trigger" default=""/>
    </params>
    <content>
<![CDATA[
<event settedUpInitially="true">
    <condition>
        <not>
            <inside objectId="#{objectId}" regionId="#{regionId}" objectPoint="all"/>
        </not>
    </condition>
    <triggers>
        #{trigger}
        <message text="#{message}"/>
        <success/>
    </triggers>
</event>
]]>
    </content>
</template>

<template name="set-robot-warzone">
    <params>
	<param name="regionId"/>
	<param name="message" default="The robot has moved out of a valid region"/>
	<param name="trigger" default=""/>
    </params>
    <content>
<![CDATA[
<use template="set-object-warzone">
    <with regionId="#{regionId}"/>
    <with message="#{message}"/>
    <with objectId="robot1"/>
    <with param="trigger">
        #{trigger}
    </with>
</use>
]]>
    </content>
</template>

Cyclic links between templates are not allowed.
A system template library for typical actions should be supported.
Thus, checking whether an object is in the region boils down to using the template defined above:

<use template="set-object-warzone" regionId="zone1" objectId="skittle" message="Object skittle not inside zone"/>

There is an environment variable TRIK_PREPROCESSOR_XML_OUTPUT, which allows you to get preprocessed xml in Constraint Parser syntax every time you load xml.