Move clipboard code from copy.go to a shared function.
All passwords are being generated with no symbols by default.

random.String expects the second argument to be false to generate a
random string with no symbols. When --nosymbols is not present, false is
passed as second argument for random.String making it generating all
passwords with no symbols by default, which is not the expected
behavior.
This commits fixes this problem by flipping nosymbols value.