keygen: Try generating the key in dart instead of using git_bindings

This seems to work rather decently, but I'm not ready to put it into
production until it is tested quite thoroughly on lots of different
platforms.

lib/ssh/keygen.dart

@@ -0,0 +1,21 @@
+import 'package:git_bindings/git_bindings.dart';
+import 'package:gitjournal/ssh/rsa_key_pair.dart';
+import 'package:gitjournal/utils/logger.dart';
+
+import 'package:meta/meta.dart';
+
+Future<String> generateSSHKeys({@required String comment}) async {
+  try {
+    var keyPair = await RsaKeyPair.generateAsync();
+    var publicKeyStr = keyPair.publicKeyString(comment: comment);
+    await setSshKeys(
+      publicKey: publicKeyStr,
+      privateKey: keyPair.privateKeyString(),
+    );
+    return publicKeyStr;
+  } catch (e) {
+    Log.e(e);
+  }
+
+  return "";
+}

lib/ssh/main_keygen.dart

@@ -0,0 +1,21 @@
+import 'dart:io';
+import 'package:gitjournal/ssh/rsa_key_pair.dart';
+
+void main() {
+  print("Generating new random key");
+  var keyPair = RsaKeyPair.generate();
+  var publicKeyStr = keyPair.publicKeyString(comment: "No Comment");
+  var privateKeyStr = keyPair.privateKeyString();
+
+  var keyName = "key_";
+  var num = 0;
+  while (File(keyName + num.toString()).existsSync()) {
+    num++;
+  }
+
+  print("Writing public key to key_$num.pub");
+  print("Writing private key to key_$num");
+
+  File("key_$num.pub").writeAsStringSync(publicKeyStr + '\n');
+  File("key_$num").writeAsStringSync(privateKeyStr + '\n');
+}