Other minor CSS issues with DRP theme

[iannesbitt]

• Icon and user name in top right of portal editor is too dark, should be #fff
  Element is .Portal.Editor #Navbar .minimal-nav > a
  

• Branding logo at bottom of portal page needs 80-100px margin-bottom to avoid footer overlap
  Element is .portal-logos-view .img-logo
  

• Logged-in drop down nav menu is extends off page right (similar to NCEAS/metacatui#1978)
  Element is .navbar-inner .dropdown-menu
  

[iannesbitt]

Reopening for two more menu issues:

• Dropdown header font color is same as background
  Element is .dropdown-header
  

• Nav dropdown is drawn behind scale bar
  Elements are: .map-view__scale-bar-container and #Navbar .dropdown-menu
  

[iannesbitt]

Moving to new issue #14