Replace Boost::foreach dependency with range-based for

[georgthegreat]

The library is marked as C++14, hence it should be safe to replace the dependency with native syntax.

boost::graph::vertices returns std::pair which is not compatible with range-based for.
As changing this behavior would result in API break, only public part was changed and the dependency still remains.

[jeremy-murphy]

Thanks!

[jeremy-murphy]

If there are any build failures, please investigate.

[georgthegreat]

@jeremy-murphy, I had to reduce the amount of changes as it turns out that range-based-for is incompatible with vertices() method (it returns std::pair which is not a range in c++ terms, yet is accepted by BOOST_FOREACH).

So, publicpart is rewritten and boost/foreach is no longer included from neither include/ nor src/ directories.

Can we merge such (partial) improvement?

[jeremy-murphy]

Whilst I think it's good to get rid of macros like BOOST_FOREACH, what I think is even better is to use algorithms in preference to for () loops. And it turns out that the implementation in Boost.Ranges does support boost::pair (and I presume std::pair) as a range. However, I don't want you to go overboard with refactoring right away, as many of these loops have large bodies, so I recommend picking the low-hanging fruit, the stuff that looks obviously like a find_if, etc.

[georgthegreat]

range-based for is much clearer to me compared to huge functional-style algorithms.

As I have failed to remove this dependency, I am closing this PR.