These replace `init()` and `tail()` which are deprecated in favour of these.
In fact, it's a good thing they're deprecated, because part of the path_prefix code involved working around a call to init() that would panic otherwise - doing the same check with an `Option` is much more ergonomic.
Previously, each time it tried to render a table (to check its width), it both re-queried the filesystem and re-formatted the values into coloured strings.
These values are now calculated only once before the table is drawn, and are used repeatedly throughout.
Although it looks as though there's more `clone()`ing going on than before, it used to be recalculating things and storing them as vectors anyway, so the memory would still be used in any case.
This commit adds --grid, which, when used with --long, will split the details into multiple columns. Currently this is just 2 columns, but in the future it will be based on the width of the terminal.
In order to do this, I had to do two things:
1. Add a `links` parameter to the filename function, which disables the printing of the arrow and link target in the details view. When this is active, the columns get way too large, and it becomes not worth it.
2. Change the `print_table` function from actually printing the table to stdout to returning a list of `Cells` based on the table. This list then gets its width measured to calculate the width of the resulting table.
Finally! The benefit of having all the field-rendering code (in details.rs) separate from the value-getting code (in file.rs) is that rendering them can be tested again.
