Generalized and simplified the logic that already kept an existing priority to also keep a date added via todo.sh -t / TODOTXT_DATE_ON_ADD (unless the replaced text also starts with a date).
- _list() now shows the capitalized filename in place of 'TODO:'.
For example, listing garden.txt produces a output prefixed by 'GARDEN:'
This eliminates the ' from $FILE' part of the _list() output. All tests
were adjusted to match this new output.
Using the cleaninput function, to escape &'s on certain actions.
Currently the actions needing escaped &'s are append, prepend and replace.
Other actions including add need unescaped &'s.
