Remove 'using namespace amx_profiler'
Make date printing optional
Pass vector by reference
Make use of the new C++11 "override" keyword
Replace plain integral TimeInterval with Duration
Drop support for alternate builds that use Boost.Chrono
Add Statistics class for statistics storage
Replace usages of plain 0 with C++11's nullptr
Add "text" format as a synonym for "txt"
Update year
Replace template argument with std::function