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.

tests/t1600-append.sh

@@ -43,6 +43,12 @@ test_todo_session 'basic append with &' <<EOF
 TODO: 1 of 1 tasks shown
 EOF
 
+echo 'jump on hay' > todo.txt
+test_todo_session 'append with spaces' <<EOF
+>>> todo.sh append 1 "and notice the   three   spaces"
+1 jump on hay and notice the   three   spaces
+EOF
+
 cat > todo.txt <<EOF
 smell the cows
 grow some corn