message: add set config methods for Context and ContextBuilder
diff: @@ -155,6 +155,11 @@ impl Context {
  };
  event
  }
  +
  + /// Sets the config
  + pub fn set_config(&mut self, conf: conf::Conf) {
  + self.conf = conf
  + }
  }
  use std::path;
  @@ -205,6 +210,12 @@ impl ContextBuilder {
  self
  }
  + /// Sets the entire config
  + pub fn conf(mut self, conf: conf::Conf) -> Self {
  + self.conf = conf;
  + self
  + }
  +
  /// Add a new read-only filesystem path to the places to search
  /// for resources.
  pub fn add_resource_path<T>(mut self, path: T) -> Self
  