Some patches for mission imports:
1. Check that the path isn't empty (the user didn't select "This PC") before continuing
2. Count successful imports
3. Avoid treating an import as a newly saved single mission unless the import was successful
Since older builds of FRED parse the mission version as a float, the version can contain a maximum of one decimal point. These changes allow FRED and FSO to disregard the build number when loading, saving, or comparing versions.
There is also a small fix to qtfred's saving of the author field.
This finally enables the `$Version:` field in FreeSpace missions, which has been present ever since the beginning of FS1's development but has never been used for its intended purpose. This field now stores the version of FSO that is required to run the mission. If the version of the engine is not sufficient to run the version of the mission, then a) the mission is hidden from the mission listing, or b) a friendly notification is displayed if the mission is loaded anyway (for example, through a campaign). Furthermore, FRED will notify the user if the mission's version is migrated from any version other than the legacy 0.10.
It will be the responsibility of coders who modify the mission format to also update the `MISSION_VERSION` constant with the appropriate major/minor/build/revision of the format change.
It's theoretically possible for `parent_type` to get out of sync with the parent's type, particularly if the parent is destroyed. Since the field is almost never used, it can be removed.
Should fix#4105.
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.
mjn-mixael