Make sure bookmarking works

[wch]

Features to check:

• Selected tab in menuItem and menuSubItem is saved. (May be related to #128.)
• Sidebar menuItem expanded state is saved.

[bborgesr]

In addition:

• Sidebar expanded/collapsed state

So, in summary, we have to add "bookmarkability" for:

• sidebar expanded/collapsed state
• menuItems expanded/collapsed state
• menuItem (or subMenuItem) that is selected/active

Possible solutions:

• give inputId, like tabsetPanel (gives bookmarkability by default). This would also address #114 (and allow us to close the corresponding PR, #128)
• create new function(s) to be used inside onBookmark and onRestore (no default bookmarkability)

Also:

• make sure this works with a dynamically generated sidebarMenu

[bborgesr]

Closed in #199