start implementing a plugin system

start implementing a plugin system using standard I/O as a transport

protobuf/plugin.proto

@@ -0,0 +1,53 @@
+syntax = "proto3";
+package deltachat_remotecontrol_bot.plugin;
+
+message Request {
+  uint32 request_id = 1;
+  oneof req {
+    PluginInitializeRequest initialize_req = 10;
+    PluginCommandListRequest command_list_req = 11;
+    PluginExecuteRequest execute_req = 12;
+  }
+}
+
+message PluginInitializeRequest {
+  string config = 1;
+}
+
+message PluginCommandListRequest {}
+
+message PluginExecuteRequest {
+  string command_id = 1;
+  repeated string arg_vector = 5;
+}
+
+message Response {
+  uint32 request_id = 1;
+  oneof res {
+    PluginInitializeResponse initialize_res = 10;
+    PluginCommandListResponse command_list_res = 11;
+    PluginExecuteResponse execute_res = 12;
+  }
+}
+
+message PluginInitializeResponse {
+  string unique_name = 1;
+  string name = 2;
+  string version = 3;
+  string authors = 4;
+}
+
+message PluginCommandListResponse {
+  repeated CommandSpec commands = 1;
+}
+
+message CommandSpec {
+  string name = 1;
+  repeated string aliases = 2;
+  string usage = 3;
+  string description = 4;
+}
+
+message PluginExecuteResponse {
+  
+}