Implemented config and crypto infrastructure (#2)

Added config file read/write infrastructure with RapidJSON.
Added key pair generation and sign/verify helper with libsodium.

src/main.cpp

@@ -4,11 +4,31 @@
 
 #include <cstdio>
 #include <iostream>
+#include "conf.h"
+#include "crypto.h"
 
 using namespace std;
 
-int main(int argc, char** argv) {
+int main(int argc, char **argv)
+{
+    if (!conf::init() || !crypto::init())
+    {
+        cerr << "Init error\n";
+        return -1;
+    }
+
+    //Example sign and verification.
+    unsigned char msg[10] = "hotpocket";
+    unsigned char *sig = new unsigned char[crypto::get_sig_len()];
+    crypto::sign(msg, 10, sig);
+
+    bool isValid = crypto::verify(msg, 10, sig);
+    if (isValid)
+        cout << "Signature verified.\n";
+    else
+        cout << "Invalid signature.\n";
 
     cout << "exited normally\n";
     return 0;
-} 
+}
+