fixing #2877 (microreference not shown in distribution references (sources))
Fixing typo in error message
fixing drupal_check_module() bug, using module_exists() instead
bugfix for #2679 (Improve Concept Relationships for Dataportal)
fixing #2679 (Improve Concept Relationships for Dataportal)
using abbreviated label for taxon relationships also in setting page (fixes one problem in #2609)
reorganizing drupal sub repository: sparate folders per version 5.x, 6.x & 7.x