[Mod support]Add new CLI options

[JimJokes]

New options: --modDir, --gameLog, --debug.
Change option --inputDir to --gameDir.

I have some free time in the next few weeks, so I plan to start making pull requests with mod support.

[truckermudgeon]

Hey @JimJokes,

Many apologies for not responding to this sooner: I've been away for the past ~5 months, and have only returned to maps development in the past two weeks.

I just wrote this in the #dev channel of the ETS2LA Discord:

since coming back, i've spent a lot of time thinking about mod support in the maps project, and reading the diffs from @JimJokes' changes: he's done an incredible job of dealing with my spaghetti code and adding support for a bunch of mods that i didn't even know existed.

ultimately, though, i'd rather not deal with adding backwards compatibility to maps, and all the stuff that brings with it (widening of types, looser constraints/guarantees about data, etc). i have to deal with so much backwards compatibility stuff in my day job, and for me, maps is meant to be an escape from things i hate about my job... it's so nice having to code for just a single (i.e., the latest) version of things.

Many apologies, again, for the time you spent breaking up your mod-support changes 😬. For now, I'd like to avoid adding mod support to maps, and instead would like to focus on my goal of writing a navigation app for myself (who only plays vanilla ATS).