Sidemenu DApps UX fixes

[alexandrashelenkova]

1. When DApp is open, the icon of that DApp should appear in the sidebar under DApp Store icon and be highlighted.
2. When user switches to another screen, the icon of the DApp should remain on the sidebar
3. Once user is back to the DApp, it should be highlighted again (no matter how user got to the screen - from sidemenu or from DApp store)
4. Show 3 most recently used DApps in the sidemenu (sorted in the alphabet order to avoid unnecessary rearrangment)

https://zpl.io/aXj8pP8

For correct UX this task should be done together with https://github.com/BeamMW/beam-dapps/issues/55

[chapati]

Since we do not have a lot of apps and 2 of them (dao & voting) are already in sidebar this can be delayed for the next version.