changed block-highlighting for errors to red

src/main/java/com/ardublock/core/Context.java

src/main/java/com/ardublock/ui/OpenblocksFrame.java

...com/ardublock/ui/listener/GenerateCodeButtonListener.java

...com/ardublock/ui/listener/SimulateCodeButtonListener.java

src/main/resources/com/ardublock/block/ardublock.properties

src/main/resources/com/ardublock/block/ardublock.xml

...ain/resources/com/ardublock/block/ardublock_de.properties