Added better handling of failures loading icons, as Cairo generated exception were crashing app under windows. Minor fix to handling missing processing params to not alter the global defaults.

clean.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+rm CMakeCache.txt
+rm install_manifest.txt
+rm -R ./CMakeFiles 
+rm -R ./rtengine/CMakeFiles
+rm -R ./rtexif/CMakeFiles
+rm -R ./rtgui/CMakeFiles
+rm -R ./rtdata/CMakeFiles
+rm ./cmake*
+rm ./rtengine/cmake*
+rm ./rtexif/cmake*
+rm ./rtgui/cmake*
+rm ./rtdata/cmake*
+rm ./Makefile
+rm ./rtengine/Makefile
+rm ./rtexif/Makefile
+rm ./rtgui/Makefile
+rm ./rtengine/librtengine.so
+rm ./rtgui/rt
+rm ./rtexif/librtexif.a