Bugs: import saved settings

The function to load saved settings doesn't work, and the building materials get mixed when importing saved work orders.

[Alistair-Afton]

I looked into both halves of this report:

1. "Load saved settings doesn't work" — if this is about work details or standing orders via gui/settings-manager, there were real bugs here that are fixed in gui/settings-manager: preserve new built-in work details scripts#1630 and gui/settings-manager: recompute unit labors after work detail import scripts#1631 (imported work details silently failed to apply to renamed built-ins, unit labors weren't recomputed, and a settings file swapped in mid-session was never re-read).

2. "Building materials get mixed when importing saved work orders" — I did an export→import→export round-trip on a fort with 226 manager orders including material conditions and material categories, and everything round-tripped exactly. To pin this down I'd need more info: which file did you import (can you attach it?), which orders/materials came out wrong, and what you expected instead?