Adds the ability to add files that already exist

Work on #16

This was a relatively large amount of work. It introduces assets which
are stored in the assets sub directory and stored in the database with
the asset type in the database.

inc/yaml

@@ -40,8 +40,8 @@ getYamlTitle(){
 }
 
 getYamlTags(){
-	vecho "getYamlTitle $*"
+	vecho "getYamlTags $*"
 	cd "$dataDir" || return
-	getYamlBlock "$1" | yq -r '.Tags | join("\n")'
+	getYamlBlock "$1" | yq -r '.Tags | if . == null then [] else . end | join("\n")'
 }