XMLReader implementation and a virtual Reader/Writer template framework.

Test_serialisation has an example of *code* *free* object serialisation
to both ostream and to XML using macro magic.

Implementing TextReader/TextWriter, YAML, JSON etc.. should be trivial
and we can use configure time options to select the default "Reader" typedef.

Present done with

"using XMLPolicy::Reader"

to pick up the default serialisation strategy.

tests/Test_serialisation.cc

@@ -0,0 +1,65 @@
+#include <Grid.h>
+
+using namespace Grid;
+
+class myclass {
+public:
+
+  GRID_DECL_CLASS_MEMBERS(myclass,
+			  int, x,
+			  double, y,
+			  bool , b,
+			  std::string, name,
+			  std::vector<double>, array,
+			  std::vector<std::vector<double> >, twodimarray,
+			  );
+
+  myclass() : array(4,5.0), twodimarray(3,std::vector<double>(2,2.0)) {
+    x=1;
+    y=2;
+    b=false;
+    name="bother said pooh";
+  }
+
+};
+
+
+uint16_t i16 = 1;
+uint16_t u16 = 2;
+uint32_t i32 = 3;
+uint32_t u32 = 4;
+uint64_t i64 = 5;
+uint64_t u64 = 6;
+float    f = M_PI;
+double   d = 2*M_PI;
+bool     b = false;
+
+int main(int argc,char **argv)
+{
+  {
+    Writer WR("bother.xml");
+
+    push(WR,"BasicTypes");
+    write(WR,"i16",i16);
+    write(WR,"u16",u16);
+    write(WR,"i32",i32);
+    write(WR,"i32",u32);
+    write(WR,"i64",i64);
+    write(WR,"i64",u64);
+    write(WR,"f",f);
+    write(WR,"d",d);
+    write(WR,"b",b);
+    pop(WR);
+
+    myclass obj;
+    write(WR,"obj",obj);
+
+  };
+
+  Reader RD("bother2.xml");
+
+  myclass copy;
+
+  read(RD,"obj",copy);
+  std::cout << "Loaded "  << copy<<std::endl;
+}