Add output folder for opale_to_pdf, clean of its input folder and rework of...

Add output folder for opale_to_pdf, clean of its input folder and rework of opale_to_pdf.ant to prevent deletion of .gitkeep files

opale_to_pdf/opale_to_pdf.ant

@@ -20,10 +20,12 @@
 	</target>
 
 	<target name="clean_everything">
-		<delete dir="../opale_to_hdoc/input"/>
-		<delete dir="../opale_to_hdoc/output/result.hdoc"/>
-		<delete dir="../hdoc_to_pdf/input"/>
-		<delete dir="../hdoc_to_pdf/output/result.pdf"/>
+		<delete>
+          <fileset dir="../opale_to_hdoc/input" excludes=".gitkeep"/>
+          <fileset file="../opale_to_hdoc/output/result.hdoc"/>
+          <fileset dir="../hdoc_to_pdf/input" excludes=".gitkeep"/>
+          <fileset file="../hdoc_to_pdf/output/result.pdf"/>
+        </delete>
 	</target>
 
 	<target name="opale_to_hdoc">