Toolbar: Select Input

[elnelson575]

This will create a single select suitable for use in toolbars.

Decisions:

• It will allow users to select a single option from a drop-down.
• It will not use Selectize.
• It will use the default menu open/close direction and formatting (vs. using selectize or adding custom JS callbacks to choose if it goes up or down)
• It will be borderless by default
• It will highlight on hover, focus, and selection
• Text will take the inherited size and match surrounding labels

[elnelson575]

Remember to put back:

    /* Ensures that inputs inherit the formatting of the toolbar and align correctly */
    /* This is particularly for select inputs inside toolbars */
    >.form-group.shiny-input-container, .form-group.shiny-input-container>* {
        width: auto;
        margin-bottom: 0;
        min-width: 0;
    }