The addition of assert functions to Userland/js
was done before we had load(..) implemented. Now
that it exists, it seems like the right move the
test helper functions to pure javascript instead
of poluting js with random global functions.
The PropertyName class able to match a number or an array can only
accept positive numerical values. However, the computed_property_name
method sometimes returned negative values.
This commit also adds a basic object access test case.
