ImageSet: added a method for intersection
S.Integers: added _eval_imageset method
Remove automatic evaluation
Added conversion to NNF
Add equals to boolean
Changed is_literal
Added tests
Fixed issues with Logical Atom
Fixed issues with count_ops and assumption
Changed count_ops and is_literal
Restructured Xor's __new__ method
Replace "except:" with "except Exception:"

Fixes #5669

Most changed, but not all; a few looked like they belonged being bare.
In particular, mpmath is not affected, nor tests.
imageset._intersect: removed the dependence on variable name
Merge pull request #7576 from clsn/bare_except

Replace "except:" with "except Exception:"
method for linear system of 3 or more eq of 1st order
Methods of linear system of 3eq and 1st order
Added linear system of n equation of 1st order
Added test cases
Made changes in linear system of 3eq 1st order type4
method for linear system of 3 or more eq of 1st order