Several things going on here:
1) refactor `get_display_string()` to `get_display_name()` to be more precise
2) likewise, refactor `alt_name` to `display_name`
3) automatically generate display names when parsing the ship, ship class, and weapon class for the first time
4) remove the on-the-fly truncation of names with hash symbols
Basically this subsumes the `end_string_at_first_hash_symbol` logic into the display name. Rather than truncate the name every time it's displayed, truncate it once when it's parsed. This takes advantage of the previous display name infrastructure, since display names are a superset of the case of truncating the hash symbol.
This also has the benefit of now allowing hash symbols within display names. When updating Destiny of Peace, I noticed that "Lockheed Shuttle #4" would no longer display properly; and it was not previously possible to fix this even with display names.
I could pull out the `get_display_string()` and `alt_name` renaming into a separate PR if desired.
This introduces a new mechanism for handling bit flags. Instead of using an int (or two, or three) to write bits into, this uses the std::bitset in a wrapper class that accepts an enum class as input. This means that certain classes of errors we've had a few of in the engine, where a coder used the wrong set of flags or checked them against the wrong variable (SF_STEALTH vs SIF_STEALTH, for example) can now be detected at a compiler level rather than not at all.
Goober5000