Removed GCode.pm
Removed the Perl bindigns for AvoidCrossingPerimeters, OozePrevention, SpiralVase, Wipe
Changed the std::set of extruder IDs to vector of IDs.
Removed some MSVC compiler warnings, removed obnoxious compiler warnings when compiling the Perl bindings.
Updated xs/Build.PL to understand BOOST_LIBRARY_PATH and
BOOST_INCLUDE_PATH environment variables. This way one may easily
switch between various boost builds.
Some minor tweeks were done to make Slic3r compile with
Visual Studio 2013.