Update BaseImageDownloader.java

Based on added an schema to support video of sdcard and it will be used to get video thumnail from the sdcard video path i.e. /storage/emulated/0/Video/VID_20141015_184740.mp4 or video of any folder.

And to get video thumnail in getView of adapter or for single image we can use it like this way

imageLoader.displayImage("video://"+imageVideoPath,holder.ivVideoThumbnail, MyApplication.options, null);

where imageVideoPath is String or Video file path i.e. /storage/emulated/0/Video/VID_20141015_184740.mp4
Merge pull request #780 from mkhan07/patch-2

Video file thumbnails support