Pass optional arguments

[alanocallaghan]

Add the ability to pass optional arguments to InstanSeg models.

Example:

  qupath.ext.instanseg.core.InstanSeg.builder()
      .modelPath("/path/to/model/")
      .arg("seed_threshold", 0.9999)
      .build()
      .detectObjects()

or equivalently

qupath.ext.instanseg.core.InstanSeg.builder()
    .modelPath("/path/to/model/")
    .args(["seed_threshold": 0.9999])
    .build()
    .detectObjects()

[petebankhead]

Think I might have inadvertently left comments pending but not submitted...

The main one is that I think we should use LinkedHashMap instead of HashMap, since insertion order could matter (even if only through a bug/regression) and I don't see any benefit in allowing HashMap to mess with this.

Also, defensive copies are cheap relative to the trouble failing to make them might cause us one day.

[petebankhead]

Ah, so that's how you do it... wanted to use a switch originally, but didn't know the syntax :)

[alanocallaghan]

You can thank IntelliJ's linting, I just alt-enter stuff and keep it if I think it's better