colors in layer chooser
minor improvement: use icons (a.o.t. text) for GUI component
fonts are not always automatically copied.. workaround
geojson does not need preview
Merge pull request #190 from nens/fritz_lizard_font

fonts are not always automatically copied.. workaround
Merge pull request #189 from nens/fritz_colors_eventlayers

colors in layer chooser for events
Merge pull request #191 from nens/dirk_use_chevron_for_table_toggling

minor improvement: use icons (a.o.t. text) for GUI component