Call getIcon if the POI provides it
Create icon based on availability
Only set location if we can match one
Increase size of labels and library names
Include the size and anchor for correct behaviour when zooming
Green marker for reference books also
Added top and bottom box-shadows
Markers for different library availability states
Removed libraryAvailability helper
Remove usage of the library template helper
Map the new library holding states to an enumeration for icons / classes

Now we make sure all holdings have an availability set since we don't
use the template helper.
Darken the unknown grey to make the text more legible