add insertion operator << definition to Store class

[marc1uk]

pretty much just boilerplate code, but it enables the possibility to Set and Get a Store into another Store without intermediate strings, which may address the underlying issue with #20 .

Test code:

// g++ -g test.cpp -I include/ -L lib/ -lStore -o testnest
#include <iostream>
#include "Store.h"

using namespace ToolFramework;

int main(){
	int a = 99;
	float b = 55.5;
	std::string s{"potato"};
	
	Store inner;
	inner.Set("a",a);
	inner.Set("b",b);
	inner.Set("s",s);
	
	std::string innerjson;
	inner >> innerjson;
	
	Store outer;
	outer.Set("inner",inner);
	
	std::string outerjson;
	outer >> outerjson;
	
	std::cout<<"Inner:\n-----"<<std::endl;
	inner.Print();
	std::cout<<"------\nAs json: '"<<innerjson<<"'\n"<<std::endl;
	
	std::cout<<"Outer:\n-----"<<std::endl;
	outer.Print();
	std::cout<<"------\nAs json: '"<<outerjson<<"'\n"<<std::endl;
	
	Store innerget;
	outer.Get("inner",innerget);
	
	std::string innergetjson;
	innerget >> innergetjson;
	
	std::cout<<"InnerGet:\n-----"<<std::endl;
	innerget.Print();
	std::cout<<"------\nAs json: '"<<innergetjson<<"'"<<std::endl;
	
	// =====================
	std::cout<<"\n==========\n"<<std::endl;
	
	
	Store outer2;
	outer2.Set("innerjson",innerjson);
	
	std::string outer2json;
	outer2 >> outer2json;
	
	std::cout<<"Outer2:\n-----"<<std::endl;
	outer2.Print();
	std::cout<<"------\nAs json: '"<<outer2json<<"'\n"<<std::endl;
	
	std::string innerjsonget;
	outer2.Get("innerjson",innerjsonget);
	
	Store innerget2;
	innerget2.JsonParser(innerjsonget);
	
	std::string inner2json;
	innerget2 >> inner2json;
	
	std::cout<<"Inner2:\n-----"<<std::endl;
	innerget2.Print();
	std::cout<<"-----\nAs json: '"<<inner2json<<"'"<<std::endl;
	
	return 0;
}

Output:

Inner:
-----
a => 99
b => 55.5
s => "potato"
------
As json: '{"a":99 ,"b":55.5 ,"s":"potato" }'

Outer:
-----
inner => {"a":99 ,"b":55.5 ,"s":"potato" }
------
As json: '{"inner":{"a":99 ,"b":55.5 ,"s":"potato" } }'

InnerGet:
-----
a => 99
b => 55.5
s => "potato"
------
As json: '{"a":99 ,"b":55.5 ,"s":"potato" }'

==========

Outer2:
-----
innerjson => "{"a":99 ,"b":55.5 ,"s":"potato" }"
------
As json: '{"innerjson":"{"a":99 ,"b":55.5 ,"s":"potato" }" }'

Inner2:
-----
a => 99
b => 55.5
s => "potato"
-----
As json: '{"a":99 ,"b":55.5 ,"s":"potato" }'