make base class for bencode related errors

src/main/java/com/mykola2312/retracker/bencode/error/BDecodeError.java

@@ -1,6 +1,6 @@
 package com.mykola2312.retracker.bencode.error;
 
-public class BDecodeError extends Exception {
+public class BDecodeError extends BError {
 	private static final long serialVersionUID = 4282658520481186036L;
 	
 	public byte[] data;

src/main/java/com/mykola2312/retracker/bencode/error/BError.java

@@ -0,0 +1,16 @@
+package com.mykola2312.retracker.bencode.error;
+
+/* A base type, all bencode related errors are
+ * derived from this class for easy try-catching
+ */
+public class BError extends Exception {
+	private static final long serialVersionUID = 1626675512183720021L;
+
+	public BError(String message) {
+		super(message);
+	}
+	
+	public BError(String message, Throwable cause) {
+		super(message, cause);
+	}
+}

src/main/java/com/mykola2312/retracker/bencode/error/BErrorNoRoot.java

@@ -0,0 +1,9 @@
+package com.mykola2312.retracker.bencode.error;
+
+public class BErrorNoRoot extends BError {
+	private static final long serialVersionUID = -7691652539624483490L;
+
+	public BErrorNoRoot() {
+		super("BTree has no root");
+	}
+}

src/main/java/com/mykola2312/retracker/bencode/error/BValueError.java

@@ -2,7 +2,7 @@ package com.mykola2312.retracker.bencode.error;
 
 import com.mykola2312.retracker.bencode.BValue;
 
-public class BValueError extends Exception {
+public class BValueError extends BError {
 	private static final long serialVersionUID = 6950892783320917930L;
 
 	public BValue node;