Disable splash screen overrides by default and add doc

src/main/resources/arsnova.properties.example

@@ -218,11 +218,15 @@ ui.slogan=Audience Response System
 # Best results are achieved with logos that have the same width and height.
 splashscreen.logo-path=resources/images/arsnova-logo.png
 splashscreen.slogan=Audience Response System
-splashscreen.slogan-color=#4A5C66
-splashscreen.background-color=#E0E0E0
-splashscreen.loading-ind-color=#4A5C66
 splashscreen.min-delay=3000
 
+# Splash screen colors
+# These settings override the default colors of the frontend theme.
+#
+#splashscreen.slogan-color=
+#splashscreen.background-color=
+#splashscreen.loading-ind-color=
+
 # Links which are displayed in the frontend applications
 #
 links.blog.url=https://arsnova.eu/blog/
@@ -272,4 +276,4 @@ pp.session-levels.en = General Education,\
 #
 tracking.provider=piwik
 tracking.tracker-url=
-tracking.site-id=
\ No newline at end of file
+tracking.site-id=

src/test/resources/arsnova.properties.example

@@ -218,11 +218,15 @@ ui.slogan=Audience Response System
 # Best results are achieved with logos that have the same width and height.
 splashscreen.logo-path=resources/images/arsnova-logo.png
 splashscreen.slogan=Audience Response System
-splashscreen.slogan-color=#4A5C66
-splashscreen.background-color=#E0E0E0
-splashscreen.loading-ind-color=#4A5C66
 splashscreen.min-delay=3000
 
+# Splash screen colors
+# These settings override the default colors of the frontend theme.
+#
+#splashscreen.slogan-color=
+#splashscreen.background-color=
+#splashscreen.loading-ind-color=
+
 # Links which are displayed in the frontend applications
 #
 links.blog.url=https://arsnova.eu/blog/
@@ -272,4 +276,4 @@ pp.session-levels.en = General Education,\
 #
 tracking.provider=piwik
 tracking.tracker-url=
-tracking.site-id=
\ No newline at end of file
+tracking.site-id=