Resolve all KatScript parameters to references during compilation

Fixes #351 (closed).

tl;dr: make myparam.T behave the same way in KatScript as &myparam.T currently does, and deprecate the & operator.

Changes all NAME tokens in KatScript to resolve to references, if possible. This will make any model parameters referenced in KatScript parse as ParameterRef. Non-model-parameters like nodes and ports will stay as-is.

This means & is no longer needed for references, because everything will now be a reference. The background to this can be read in the comments of #351 (closed), but in short, we decided the previous "pass by value" behaviour (e.g. with myparam.T) is almost never useful, and also probably not what the user expects.

The & operator remains supported, but is now a no-op. If it's used, a warning is printed telling the user this will not be supported in a future release. We should eventually make use of & a syntax error, and a new issue should be created to track this removal.

Side-effects to this change:

• The directives that previously expected parameters to be passed by value, e.g. the target of an xaxis or lock, now get references. I had to modify the lock action to handle this, but xaxis seemed to already work without modification. This probably needs some discussion on how best to really solve.