Add restore config

* R/mix.R(read_conf): New function.

* R/shiny-ui-base.R(conf2rv_conf): New function.
  In order to save config as yaml function, the reactive form of
  config must be converted to a list.

 (input$restoreConfB): New observer.

* R/shiny-ui-base.R(server_conf), R/shiny-ui-top.R(server): Now that
  we update rv inside server_conf, it must return it in some way.