Code folding in the XML DSLs

Summary

Due to the nature of XML, such files can be noisy and unnecessarily long, so some code folding could help this case and lessen the cognitive load and comprehension of Citrus XML test files.

One simple example would be the echo action. The code folding could turn

<echo>
  <message>Some message to print</message>
</echo>

into

<echo>Some message to print</echo>

and hide the <message> tags.

Tasks

Collect the tags that could be folded.
Implement code folding. It might be something similar that goes on in the Just Kitting plugin.

Folding candidates

[x] echo in XML and Spring XML


<echo>
<message>Some message to print</message>
</echo>

Some message to print


- [x] load properties in XML and Spring XML
```xml
<load>
  <properties file="classpath:some/file" />
</load>

<load properties: classpath:some/file />

[x] receive.message.builder with @file in Spring


<receive endpoint="myMessageEndpoint">
<message>
    <builder type="groovy" file="classpath:org/citrusframework/actions/payload.groovy"/>
</message>
</receive>


- [x] send.message.builder with `@file` in Spring
```xml
<send endpoint="myMessageEndpoint">
    <message>
        <builder type="groovy" file="classpath:org/citrusframework/actions/payload.groovy" />
    </message>
</send>

<send message "classpath:org/citrusframework/actions/payload.groovy" to "myMessageEndpoint" />

[x] receive.message.validate.script with @file in Spring


<message>
<validate>
    <script type="groovy"
            file="classpath:org/citrusframework/jms/integration/helloValidationScript.groovy"/>
</validate>
</message>


- [x] receive.validate.script with `@file` in non-Spring
```xml
<validate>
  <script type="groovy" file="classpath:some/file" />
</validate>

<validate by groovy script "classpath:some/file" />

[x] purge-jms-queues.queue (without attributes) in XML and Spring XML (http://www.citrusframework.org/schema/jms/testcase).
- [x] Same is true for the purge-channels.channel tags
- [x] and the purge-endpoint.endpoint tags.
```
<jms:purge-jms-queues>
<jms:queue ref="myQueue"/>
<jms:queue name="JMS.Queue.1"/>
</jms:purge-jms-queues>
```

<jms:purge-jms-queues ref:myQueue, name:JMS.Queue.1 /> or <jms:purge-jms-queues myQueue, "JMS.Queue.1" />


- [x] Camel remove/start/stop routes at
  - [x] remove-routes.route
  - [x] start-routes.route
  - [x] stop-routes.route tag in Spring
```xml
<camel:remove-routes camel-context="camelContext">
  <route id="route_1"/>
  <route id="route_2"/>
  <route id="route_3"/>
</camel:remove-routes>

<camel:remove-routes in "camelContext": "route_1", "route_2", "route_3" />

picimako / citric