Adding support for custom files

Dockerfile

@@ -20,4 +20,8 @@ RUN \
     && rm -rf /tmp/orbeon
 
 COPY ./$flavour/tomcat/ /usr/local/tomcat/
-COPY ./$flavour/orbeon/ /usr/local/orbeon/
+COPY ./$flavour/orbeon/ /usr/local/orbeon/
+
+COPY ./custom/tomcat/ /usr/local/tomcat/
+COPY ./custom/orbeon/ /usr/local/orbeon/
+COPY ./custom/resources/ /usr/local/custom/resources/

custom/orbeon/README.txt

@@ -0,0 +1,2 @@
+Files (and directories) which will override the default Orbeon files
+

custom/resources/README.txt

@@ -0,0 +1,2 @@
+Files (and directories) which will be copied to /usr/share/custom/resources
+

custom/tomcat/README.txt

@@ -0,0 +1 @@
+Files (and directories) which will override the default tomcat files