Refactoring

Today I began implementing some more improvements to the existing wrapper classes suggested by Bill / John Cremona. First I added "complex component access" functionality to all classes where it makes sense. The easiest example is fmpqxx. The following all work:

fmpqxx a(3, 4u);

a.num() = 5;

std::cout << (a+a).num() << '\n';

 In particular, depending on the object type, num() will return a reference to the denominator, or constant reference, or an expression template.

After that, I began adding member functions for all global functions. So one can e.g. do a.divrem(b) instead of divrem(a, b). As is to be expected, this process is quite laborious (simply because there are a lot of functions in flint), and I will have to continue it tomorrow. Then I will also update the documentation.