This commit (obviously non-atomic) cleans LIEF's code base by:
- Using pointer semantics (`std::unique_ptr<>`)
- Using LEAF boost error in the binary stream
- Reducing the scope of the iterators (`it_section`, ...)
- Removing `Structures.hpp` from the public headers
- etc
* JSON visitor are located in the format namespace
* Visitor are *real* visitor
* Visitable class has been renamed to Object
* Due to a bug in Visual Studio 2015, we move to VS2017
Romain Thomas