删除无用代码，加入RPC调用

pb/shotrdp.proto

@@ -0,0 +1,16 @@
+syntax = "proto3";
+option go_package = "shotrdp/pb";
+
+package pb;
+
+message Request {
+  string host = 1;
+}
+
+message Response {
+  bytes image_bytes = 1;
+}
+
+service GetScreen {
+  rpc GetScreen (Request) returns (Response);
+}