Merge pull request #914 from mattermost/plt-297

PLT-297 Add ability to override username and icon for posts from incoming webhooks.

model/config.go

@@ -29,6 +29,8 @@ type ServiceSettings struct {
 	GoogleDeveloperKey         string
 	EnableOAuthServiceProvider bool
 	EnableIncomingWebhooks     bool
+	EnablePostUsernameOverride bool
+	EnablePostIconOverride     bool
 	EnableTesting              bool
 }