feat: add csharp interop code generation but no test.

- add csharp interop code generation without testing.
- add annotation for bmap binding project.
- fix README.

CodeGen/BMapBindings/ExpFctParamDecl.java

@@ -1,16 +1,48 @@
 
+/**
+ * The class represent a single parameter (argument) of function. This class
+ * usually is the member of {@linkplain ExpFctDecl}.
+ */
 public class ExpFctParamDecl {
-	
+
+	/**
+	 * The type of this parameter.
+	 */
 	public VariableType mVarType;
+	/**
+	 * The name of this parameter.
+	 */
 	public String mVarName;
+	/**
+	 * True if this paramter is marked as input parameter, otherwise false.
+	 * <p>
+	 * Input parameter and output paramter is commonly used in C/C++ code. By using
+	 * this feature, each function can receive multiple arguments and return
+	 * multiple arguments without defining a struct to hold it.
+	 * <p>
+	 * The type of input parameter is itself. However, the type of output parameter
+	 * is the pointer of itself. So you may need get its pointer type when
+	 * processing output paramter, especially for the scenario that the target
+	 * language do not support explicit output parameter keyword.
+	 */
 	public boolean mIsInput;
+	/**
+	 * The description of this parameter.
+	 * <p>
+	 * This description is generated by this program. It will indicate the
+	 * underlying C++ type to tell end user how to treat this paramter because some
+	 * target languages' native calling style can not represent these detail.
+	 * <p>
+	 * In this program, this field must be written as a annotation of corresponding
+	 * function.
+	 */
 	public String mVarDesc;
-	
+
 	public ExpFctParamDecl() {
 		mVarType = new VariableType();
 		mVarName = "";
 		mVarDesc = "";
 		mIsInput = true;
 	}
-	
+
 }