- Continued refactoring of address decoding.

- Device read and write may now throw MemoryAccessException, and appropriate
  throws clauses have been added throughout the code.

src/test/java/com/loomcom/symon/MemoryRangeTest.java

@@ -2,9 +2,6 @@ package com.loomcom.symon;
 
 import junit.framework.*;
 
-import java.util.HashMap;
-import java.util.Map;
-
 import com.loomcom.symon.exceptions.*;
 
 /**