Highlight read

[Shin-703]

This is an answer to the issue #7 highlight read. This enhancement adds highlights when explicitly reading data (in data segment or register block) while executing step by step.

There is now two colors for these highlights (configurable by the user), blue for explicit reading and redish for explicit writing.

[privat]

There are some errors on my machine, maybe some settings are not initialized properly

$ java -jar rars.jar 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "java.awt.Color.equals(Object)" because "<local3>" is null
	at rars.venus.settings.SettingsHighlightingAction.initializeButtonColors(SettingsHighlightingAction.java:341)
	at rars.venus.settings.SettingsHighlightingAction.buildDialogPanel(SettingsHighlightingAction.java:175)

[privat]

it works \o/ :tada: