Update link to public Git repo in Python bindings
Pseudo-mutable data table variant iterators for primitives, in preparation for variant fallbacks
Add variant specialisation for data table column variant iterator
Add support for more than 10 columns
Amend test for data tables with a large number of columns
Variable time resolution for data table performance test, via Boost.Chrono
Fixes broken VC10 (VS 2010) compilation caused by separating call_if decl/def into .hpp/.ipp files