use super's free_symbols and is_number
change Product and Sum _eval_is_zero to proprty

I don't know why having _eval_is_zero for Integral works but this
doesn't work for these two objects.
Revert "make is_positive and is_negative like new assumptions"

This reverts commit 01a4546561cfcdb494d85a885bc151f7a7dfd34e.
Revert "change Product and Sum _eval_is_zero to proprty"

The reason that the _eval_is_zero were not working is that
the evaluation of the new is_positive and is_negative were able to figure
out the value of the integral. As long as they *don't* do that then
the _eval_is_zero will work; otherwise naming them as is_zero routines
will short-circuit the full assumptions engine.

This reverts commit ce0ccf7dd20da4b11614962467699523ffec32b5.