added closesilently command for modmail

largely refactored modmail future handling and error handling in case:
no permission, unable to contact user
fixed help command template

abstracto-application/abstracto-modules/modmail/modmail-impl/src/main/resources/templates/exception/modmail_exception_cannot_delete_channel_embed_en_US.ftl

@@ -0,0 +1,12 @@
+{
+  "author": {
+    "name": "${user.member.effectiveName}",
+    "avatar":  "${user.member.user.effectiveAvatarUrl}"
+  },
+  "color" : {
+    "r": 200,
+    "g": 0,
+    "b": 255
+  },
+  "description": "<#include "close_failed_to_delete_text_channel">"
+}

abstracto-application/abstracto-modules/modmail/modmail-impl/src/main/resources/templates/exception/modmail_exception_generic_embed_en_US.ftl

@@ -0,0 +1,12 @@
+{
+  "author": {
+    "name": "${user.member.effectiveName}",
+    "avatar":  "${user.member.user.effectiveAvatarUrl}"
+  },
+  "color" : {
+    "r": 200,
+    "g": 0,
+    "b": 255
+  },
+  "description": "<#include "modmail_generic_error">"
+}

abstracto-application/abstracto-modules/modmail/modmail-impl/src/main/resources/templates/modmail/modmail_closing_user_message_embed_en_US.ftl

@@ -0,0 +1,8 @@
+{
+  "color" : {
+    "r": 200,
+    "g": 0,
+    "b": 255
+  },
+  "description": "<#include "modmail_closing_user_message_description">"
+}