task-data-plugin: identify segments with "red marked" terms

this segment should set the custom segment-alternative-attribute "missingTargetTermOnImport" for all segments with red-marked terms. As a value of the attribute it sets the number of red-marked terms in the segment (if 2 terms are marked red in the source, the number is 2)

As planned for all task-data-plugins, this plugin in the future should be callable

• after each import via system-config (sufficient in 2014)
• by a dedicated call of another process
• via REST-API.