support all flavors of the update-json format

[NikkyAI]

https://mcforge.readthedocs.io/en/latest/gettingstarted/autoupdate/#update-json-format

to install forge i already use their format

http://files.minecraftforge.net/maven/net/minecraftforge/forge/json

foamfix, charset and other update json files

https://asie.pl/files/minecraft/update/foamfix.json
https://asie.pl/files/minecraft/update/charset.json
https://github.com/williewillus/Botania/blob/master/version/update.json

foamfix and charset require a url template

forge

forge has a vastly different structure
it defines webpath for the url template +1
promos keys are standard, but they point to the "number" mapping containing
a artifact/build object with the following useful values:

• mcversion
• forgeversion
• branch

a code snippets says more then a thousand words.. well not quite.. but lets try anyway

var longVersion = "${mcversion}-${forgeVersion}"
if (branch != null) {
    longVersion += "-$branch"
}
val fileName = "forge-${longVersion]-installer.jar"
val url = "${webpath}/${longVersion}/${fileName}"

foamfix, charset etc..

these do notdefine a webpath or enough information to put together a url template
worst case the only contains promos which leads to a version string eg. "0.9.1"
and user input is required

http://asie.pl/files/mods/FoamFix/foamfix-${version}-${mcversion}-anarchy.jar

todo

look at more examples
it seems like there is only 2 formats.. just forge doing their own extension / thing which could be supported by setting the url template to a magic value
but there might be more mods doing their own standards

[NikkyAI]

implemented, forge might be merged in later