add_ui_sidebar_basic: Add UI Elements to the Sidebar (Basic Tab)
Description
This function registers UI elements to the primary (front-most) tab
on the dashboard sidebar. The default name of the tab is Basic but
can be renamed using the tabname argument. This tab will be active on the
sidebar when the user first opens the shiny application.
whether to append the elementlist to currently
registered elements or replace the currently registered elements.
tabname
change the label on the UI tab (default = "Basic")
Shiny Usage
Call this function after creating elements in ui_sidebar.R to register
them to the application framework and show them on the Basic tab in the
dashboard sidebar