Removed a broken Arc Fitting feature.

Removed the questionable Pressure Advance feature. It is better to use the Pressure Advance implemented into a firmware.
Added a C++ implementation of GCodeReader and SpiralVase, thanks to @alexrj
Added a C++ implementation of GCodeTimeEstimator, thanks to @lordofhyphens

xs/xsp/GCode.xsp

@@ -4,6 +4,7 @@
 #include <xsinit.h>
 #include "libslic3r/GCode.hpp"
 #include "libslic3r/GCode/CoolingBuffer.hpp"
+#include "libslic3r/GCode/SpiralVase.hpp"
 %}
 
 %name{Slic3r::GCode::AvoidCrossingPerimeters} class AvoidCrossingPerimeters {
@@ -81,6 +82,18 @@
     std::string flush();
 };
 
+%name{Slic3r::GCode::SpiralVase} class SpiralVase {
+    SpiralVase(StaticPrintConfig* config)
+        %code{% RETVAL = new SpiralVase(*dynamic_cast<PrintConfig*>(config)); %};
+    ~SpiralVase();
+    
+    bool enable()
+        %code{% RETVAL = THIS->enable; %};
+    void set_enable(bool enable)
+        %code{% THIS->enable = enable; %};
+    std::string process_layer(std::string gcode);
+};
+
 %name{Slic3r::GCode} class GCode {
     GCode();
     ~GCode();