Add _eval_is_algebraic helpers for re/im/conjugate/abs

fixes #8656
Rewrite Gamma as Factorial #8621

Code quality improved for pull 8700
Merge pull request #8700 from aktech/issue#8621

Function to Rewrite Gamma as Factorial #8621
Merge pull request #8699 from skirpichev/8656-fix

Add _eval_is_algebraic helpers for re/im/conjugate/abs
Modified default range to interpret the assumptions of free_vars

Currently plot has a default range of (-10,10) when user doesn't
provide a range. However this default behaviour doesn't care about the
properties/assumptions of the free_variables. This commit corrects
this situation for two such cases, ie, when the variable is positive
and when it is negative.