Make the `rest()` function aware of `@p.X` and `@p['X']` (breaking change)

[nblumhardt]

Fixes #107

The existing behavior was intended to allow @p.X to be an escape hatch so that the reference to X is invisible to rest(). This turns out to be confusing in actual use.

The new ways to hide a property reference from rest() are:

let p = @p in p.X

or

@p[concat('X', '')]

etc.

Major version bump because this is likely to affect a few templates in use.