Added convenience functions for constructing objects from a row

[dend456]

Added a template function that allows you to retrieve all columns (or first N columns) of a row as an object. Extremely convenient when working with a table that has a large number of columns. Instead of having to do:
int i0 = query.getColumn(0);
int i1 = query.getColumn(1);
...
int i39 = query.getColumn(39);

then passing all those temporary variables into a constructor, you can do:

auto i = query.getColumns<MyClass, 40>();

where MyClass has a constructor that takes 40 arguments that are convertible from a Column object.

[coveralls]

Coverage remained the same at 96.231% when pulling f01a644 on dend456:master into 92bbecc on SRombauts:master.

[SRombauts]

Hi @dend456,

Thanks a lot, this is great!

And thanks for providing unit-tests without me asking for it :)

Cheers!

[dend456]

Np, do you think a function that fills a std::vector from all rows in the result would be useful?

[SRombauts]

Well, it could, but the problem are:

1. you would like to be able to use any container
2. I am often using container of unique or shared ptr

(what I mean is that this could lead to a complex template with multiple paramters)