Don't repeat yourself. These property reading routines are actually
methods on the PartialConfig struct, so make them *actually* methods.
Because the table doesn't know it's own name, the path-specific config
needs to be updated with that external knowledge.
The `lconf()` function will eventually load the whole file, but for now
it reads in only the "[all]" table.
That "[all]" table will be used as the global fallback when per-project
settings are left unspecified.
The unit test "passes" but only because I've discarded those per-project
configs from the expected result. This is just so I can see clearly that
the all-table is loading properly.
The get_property function needs to say that there is no property so that
the caller can respond appropriately. I'm going to need to frequently
respond to the "no such property" path by treating it as *not* an error.
If the config file doesn't specify a property, that's not an error, it's
just not specified and the default should be used instead. This util fn
makes that a bit more ergonomic.
I don't want to remember to construct a `String` every single time I
want to call this function with a string literal. So I won't.
Make the functions generic over anything that implements the ToString
trait.
