added server endpoint to get server version, added errorhandling for update check

...budgetmaster/logic/serverconnection/ServerConnection.java

src/de/deadlocker8/budgetmaster/logic/utils/Strings.java

...adlocker8/budgetmaster/resources/languages/_de.properties

...adlocker8/budgetmaster/resources/languages/_en.properties

...de/deadlocker8/budgetmaster/ui/controller/Controller.java

src/de/deadlocker8/budgetmasterserver/main/Main.java

...de/deadlocker8/budgetmasterserver/server/SparkServer.java

...locker8/budgetmasterserver/server/version/VersionGet.java