Allow adding to existing monster groups in json

[glamcube17]

Currently, there is no way for a mod to modify the contents of a monster group without entirely overriding it. This makes it... rather difficult to get modded monsters to show up in existing locations. And by "rather difficult" I mean "this PR was the easiest way".

For situations where entirely overriding the group is desired, adding "override": true will result in the old behavior of discarding the existing contents.

Additionally, "freq_total": int and "auto_total": true change the maximum number to "roll" for spawns, rather than it being hardcoded at 1000. freq_total changes it to the number specified, while auto_total changes it to the sum of each entry's frequencies.

[DracoGriffin]

Think you need a space after false here , false )

[DracoGriffin]

And I think "default" needs space on either side jo.has_string( "default" )

[glamcube17]

Fixed, along with splitting a line that was too long. That should be all the astyle issues from what I could tell.

[ZhilkinSerg]

Can you please use it in some mod as an example?

[glamcube17]

Say you wanted to make bunnies sometimes spawn instead of zombies earlygame. You could do:

{
    "type":"monstergroup",
    "name":"GROUP_ZOMBIE",
    "freq_total": 1300,
    "monsters": [
      { "monster" : "mon_rabbit", "freq" : 150, "cost_multiplier" : 5 },
      { "monster" : "mon_rabbit", "freq" : 100, "cost_multiplier" : 15, "pack_size": [2,4] },
      { "monster" : "mon_rabbit", "freq" : 50, "cost_multiplier" : 25, "pack_size": [6,12] }
    ]
}

Or maybe you think mansions are too easy and want to turn them into a hellscape nightmarezone:

{
    "type":"monstergroup",
    "name":"GROUP_MANSION",
    "override": true,
    "auto_total": true,
    "default": "mon_null",
    "monsters": [
      { "monster" : "mon_blob_small", "freq" : 500, "cost_multiplier" : 2, "pack_size": [3,6] },
      { "monster" : "mon_blob", "freq" : 300, "cost_multiplier" : 5, "pack_size": [1,2] },
      { "monster" : "mon_blob_large", "freq" : 200, "cost_multiplier" : 7 },
      { "monster" : "mon_shoggoth", "freq" : 10, "cost_multiplier" : 30 },
      { "monster" : "mon_shoggoth", "freq" : 1, "cost_multiplier" : 300, "pack_size": [1,100], "//":"1d100 shoggoths" }
    ]
}

Or maybe you want mininuke hacks to occasionally spawn in the forest for some reason:

{
    "type":"monstergroup",
    "name":"GROUP_FOREST",
    "freq_total": 1001,
    "monsters": [
      { "monster" : "mon_mininuke_hack", "freq" : 1, "cost_multiplier" : 50 }
    ]
}

The second would be possible to do the way it currently works, but the first and third would require reproducing the whole list and scaling them proportionally to the ones you're adding.