BUG: Multiple whitespace was condensed, CR/LF not turned to space.

Missing quoting inside cleaninput() condensed multiple subsequent spaces into a single space, even when the user took pains to preserve whitespace by properly quoting the task in the shell.
The 'tr' command completely removed CR and LF characters instead of replacing them with a single space.
Add test cases for the whitespace handling to the add, append, prepend and replace actions.

todo.sh

@@ -269,7 +269,7 @@ cleaninput()
 {
     # Cleanup the input
     # Replace newlines with spaces Always
-    input=$(echo $input | tr -d '\r\n')
+    input=`printf %s "$input" | tr '\r\n' ' '`
 
     if [ "$1" = "for sed" ]; then
         # This action uses sed with "|" as the substitution separator, and & as