Custom run configuration builder cannot create XML data with nested objects

[rodionmoiseev]

For example the setting that is supposed to generate (note the nested elements in tasks node):

<configuration default="false" name="watch">
      <node-options />
      <gulpfile>$PROJECT_DIR$/cell/www/gulpfile.js</gulpfile>
      <tasks>
        <task>css</task>
        <task>js</task>
        <task>watch</task>
      </tasks>
      <arguments />
      <pass-parent-envs>true</pass-parent-envs>
      <envs />
      <method />
    </configuration>

actually generates:

    <configuration default="false" name="Watch" >
      <log_file path="$PROJECT_DIR$/services/cell/log/cell.log" />
      <node-options />
      <gulpfile>$PROJECT_DIR$/cell/www/gulpfile.js</gulpfile>
      <tasks />
      <arguments />
      <envs />
      <method />
    </configuration>