Added the ability to untag media files in core.

core/src/main/groovy/com/jdbernard/wdiwtlt/db/ORM.groovy

@@ -811,6 +811,24 @@ public class ORM {
                             params)
                         sql.executeInsert(insertQuery, params) } } } } }
 
+    public def untagMediaFiles(List<Integer> mediaFileIds,
+    List<String> tagNames) {
+
+        withTranscation {
+            List<Tag> tags = tagNames.collect(getTagByName).findAll()
+            def tagPlaceholders = tags.collect { '?' }.join(', ')
+            def tagIds = tags.collect { it.id }
+
+            String deleteQuery = """
+                DELETE FROM media_files_tags
+                WHERE tag_id IN ($tagPlaceHolders) AND media_file_id = ?"""
+
+            mediaFileIds.each { mfId ->
+                def params = tagIds + mfId
+                logger.debug('Removing tags.\n\tSQL: {}\n\tPARAMS: {}',
+                    deleteQuery, params)
+                sql.execute(deleteQuery, params) } } }
+
     /// ### Utility functions
     public def withTransaction(Closure c) {
         try { sql.execute('BEGIN TRANSACTION'); return c() }