Allow for any order of model and formula args

[falkecarlsen]

Would be nice to allow the following syntax as the improvements from #224 makes model and formula args positional:

./cgaal check model.lcgs query.atl
./cgaal check query.atl model.lcgs

And for #217 also:

./cgaal check model.lcgs query0.atl query1.atl query2.atl

Detection of type would need to be with extension (.atl,lcgs) for JSON, we could attempt to parse the input, to determine its type. This adds a bit of overhead, but minimal, and only for JSON input files.

[NicEastvillage]

I am not sure I want this feature. It adds a tiny quality-of-life feature for users, but a lot of trouble for us, the developers. Trouble that we are going to have to deal with every time we want to change the CLI in the future.

As you mentioned, JSON files (but also extensionless files) must be parsed to determine which is the model and which is the property. If we at some point want to allow another file format (e.g. PRISM), then this problem becomes worse.

For #217 with multiple property files, it only makes sense to have the properties last. I do not want to have to find the model among N paths.