Renamed NeConvertAtom to a better name.
Fixed output of trace.
Backquotes, commas and comma-ats are displayed in short form.
Fixed 'append' native and substring tests.
Native 'eval' now takes an environment value.
Fixed bug in 'parent'.

It was returning an invalid table and not nil when the table had no parent.
Fixed some comments.
Added extra check in native 'eval'.