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/t1100-replace.sh

@@ -89,6 +89,14 @@ TODO: Replaced task with:
 1 thrash the hay & thrash the wheat
 EOF
 
+echo 'jump on hay' > todo.txt
+test_todo_session 'replace with spaces' <<EOF
+>>> todo.sh replace 1 "notice the   three   spaces"
+1 jump on hay
+TODO: Replaced task with:
+1 notice the   three   spaces
+EOF
+
 cat > todo.txt <<EOF
 smell the cows
 grow some corn