This commit converts script query to use a new FilterScript context. The
new context returns a boolean, so the error that would have previously
happened at runtime if a non boolean was returned would now happen at
script compilation. Also, the leniency of supporting returning a number
and 0 mapping to false, non-zero to true is gone, but it was never
documented. With the new context compilation will now also fail if
special variables are used at compilation time, instead of runtime, eg
ctx.
96b0d3e0cc