freeimagedec: Move utility functions to gstfreeimageutils.c/.h and other minor cleanup

Also removed static pad templates, changed elements to have underscore rather than hyphen in their name, and fix caps handling (BGR/RGB)

ext/freeimage/gstfreeimageutils.h

@@ -0,0 +1,16 @@
+#ifndef __GST_FREEIMAGEUTILS_H__
+#define __GST_FREEIMAGEUTILS_H__
+
+#include <gst/gst.h>
+#include <FreeImage.h>
+
+GstCaps * gst_freeimageutils_caps_from_dib (FIBITMAP * dib,
+    gint fps_n, gint fps_d);
+GstCaps * gst_freeimageutils_caps_from_freeimage_format (
+    FREE_IMAGE_FORMAT fif);
+
+gboolean gst_freeimageutils_parse_caps (const GstCaps * caps,
+    FREE_IMAGE_TYPE * type, gint * width, gint * height, gint * bpp,
+    unsigned * red_mask, unsigned * green_mask, unsigned * blue_mask);
+ 
+#endif // __GST_FREEIMAGEUTILS_H__