First of paragraph of Classes and Structures

First of paragraph of Classes and Structures is finished.
start "Patterns"
[语法总计]占坑 第三章 Summary of the Grammar
整理语句列表
[语法总计]占坑 第三章 Summary of the Grammar
整理语句列表
finish bitwise not or and xor
[语法总计]占坑 第三章 Summary of the Grammar
整理语句列表
complete (Summary of the Grammar) structure
merge changes
Started Definition Syntax in Chapter 09
修改一些表达方式。
占坑 Control Flow: Conditional Statements
make consistent with the previous chapter
add more translate
翻译控制流一章（未完）
统一符号使用
Merge branch 'develop' of https://github.com/xielingwang/the-swift-programming-language-in-chinese into develop
完成Conditional Statements的翻译。