Whereas previously we would say:
```
target/debug/arti: error: invalid escape character in string: `Z` at line 9 column 14 in ../../.config/arti/arti.toml
```
we now say:
```
target/debug/arti: error: invalid escape character in string: `Z` at line 9 column 14 in ../../.config/arti/arti.toml (If you wanted to include a literal \ character, you need to escape it by writing two in a row: \\)
```
The implementation is a bit of a hack, I'm afraid, but I don't think
it's all that bad.
Closes#549.
The parameter to FileWatcher::new is not a polling time fallback; it
is a "debounce time". Events are always delayed by at least this
much.
10s is much too long for this. 1s is more appropriate.
We're going to need to do config file reading in two phases.
Right now this isn't actually necessary, because the set of files
is fixed since we don't support dynamically scanning directories.
But the new API will be needed in a moment.
Code motion and API changes, but no overall functional change.
Review with `git show -b` may be helpful.
The new API also provides for dealing with directories, but right now
that doesn't happen.