ATS-812: PoC FFmpeg skeleton - experiments

- add PoC option to convert from mp4 to either image/png or image/png
- single frame based on timeOffset param (example format "00:00:00.5")
- transform option names & support mimetypes subject to change
- requires detailed design + (unit) regression tests

- see also MM-156

alfresco-transformer-base/src/main/java/org/alfresco/transformer/util/RequestParamMap.java

@@ -72,4 +72,7 @@ public interface RequestParamMap
     String INCLUDE_CONTENTS        = "includeContents";
     String NOT_EXTRACT_BOOKMARK_TEXT = "notExtractBookmarksText";
     String PAGE_LIMIT              = "pageLimit";
+
+    // TODO PoC for FFmpeg
+    String TIME_OFFSET             = "timeOffset";
 }